People can have a variety of reasons for saying particular books are favorites, but I mostly apply that label to the books I've reread the most times. This unavoidably biases the label to older books that I have had more time to reread, but it works pretty well for most of my reading. About 3/4 of my logged rereads are the complete books, and about 1/4 are various portions (bits, end, most, much, part, parts, skim, some). I usually don't even log a quick look at a scene or two.
I started keeping a log of my reading in 1975, and have kept it fairly well ever since, though there were years that I didn't log stories read in magazines. For many years, about a third of my reading was rereading, but that fraction has gone down in recent years as the pressure of the tbr list has increased and time available hasn't. Last year, only about 16% of the books in my log were rereads. I record humor scores (on a scale from -1 to +5) for the romances I read (a list is available here), because I preferentially seek romances with humor. Humor is only a selection criterion for a subset of my F&SF reading, which I have been doing a couple decades longer than romance reading, so I don't record humor scores for F&SF.
These are my most reread books (based on parsing my reading log), in descending order of times read (cutting off at 5 readings), with first year and most recent year read, and humor scores for romances (an objective record of a subjective reaction). The genre is between the title and author: (r) Romance, (s) F&SF, (sr) Short Romance, (ss) Short F&SF. The list is a snapshot early in 2021.
28 A Rake's Reform (r) Holbrook, Cindy (1995-2019) *****
26 Ravished (r) Quick, Amanda (1995-2021) *****
24 Agent of Change (s) Lee, Sharon & Miller, Steve (1988-2009)
24 Lord Kalvan of Otherwhen (s) Piper, H. Beam (1977-2015)
23 Black Sheep (r) Heyer, Georgette (1993-2018) ****
23 Carpe Diem (s) Lee, Sharon & Miller, Steve (1989-2009)
22 The Secret (r) Garwood, Julie (1995-2015) ****
22 The Mad Miss Mathley (r) Martin, Michelle (1995-2019) *****
22 Conflict of Honors (s) Lee, Sharon & Miller, Steve (1988-2009)
21 The Lion's Lady (r) Garwood, Julie (1995-2020) *****
21 Masters of Space (s) Smith, Edward E. & Evans, E. E. (1978-2020)
19 Lord Sayer's Ghost (r) Holbrook, Cindy (1996-2019) *****
19 Subspace Explorers (s) Smith, Edward E. (1978-2020)
19 Path of the Fury (s) Weber, David (1993-2017)
18 Christmas Wishes (r) Metzger, Barbara (1993-2019) ****
18 Dangerous (r) Quick, Amanda (1995-2016) ***
18 Restoree (s) McCaffrey, Anne (1976-2014)
17 These Old Shades (r) Heyer, Georgette (1993-2011) ****
17 The I Inside (s) Foster, Alan Dean (1984-2016)
17 A Planet for Texans (s) Piper, H. Beam & McGuire, John J. (1976-2017)
17 Subspace Encounter (s) Smith, Edward E. (1983-2020)
16 The Bride (r) Garwood, Julie (1995-2006) ****
16 Devil's Cub (r) Heyer, Georgette (1993-2011) ****
16 Autumn Glory (sr) Metzger, Barbara (1994-2004)
15 Elyza (r) Darcy, Clare (1993-2017) ****
15 The Actress & the Marquis (r) Holbrook, Cindy (1997-2019) *****
15 Mistress (r) Quick, Amanda (1995-2016) ***
15 Scandal (r) Quick, Amanda (1995-2008) ***
15 The Shockwave Rider (s) Brunner, John (1976-2021)
15 The Stone That Never Came Down (s) Brunner, John (1975-2018)
15 The Apocalypse Troll (s) Weber, David (2000-2017)
15 Healer (s) Wilson, F. Paul (1977-2017)
14 Frederica (r) Heyer, Georgette (1993-2020) ****
14 The Corinthian (r) Heyer, Georgette (1993-2015) ****
14 The Duke's Downfall (r) Lynson, Jane (1996-2020) *****
14 Deception (r) Quick, Amanda (1995-2014) ****
13 Laugh With Me, Love With Me (r) Damon, Lee (1997-2017) ****
13 Honor's Splendour (r) Garwood, Julie (1995-2005) ***
13 The Unknown Ajax (r) Heyer, Georgette (1993-2020) ****
13 Venetia (r) Heyer, Georgette (1993-2014) ***
13 The Cruachan and the Killane (s) Cristabel (1976-2003)
13 The Prodigal Sun (s) High, Philip E. (1978-2021)
13 Skylark Duquesne (s) Smith, Edward E. (1977-2020)
13 Skylark of Valeron (s) Smith, Edward E. (1977-2020)
12 Prince Charming (r) Garwood, Julie (1995-2021) ***
12 A Suspicious Affair (r) Metzger, Barbara (1994-2019) ****
12 Cupboard Kisses (r) Metzger, Barbara (1993-2019) ****
12 The Tenacious Miss Tamerlane (r) Michaels, Kasey (1994-2014) *****
12 Rendezvous (r) Quick, Amanda (1995-2017) ***
12 The Cross-Time Engineer (s) Frankowski, Leo (1986-2020)
12 Reality Forbidden (s) High, Philip E. (1979-2013)
12 The Time Mercenaries (s) High, Philip E. (1979-2021)
12 These Savage Futurians (s) High, Philip E. (1979-2021)
12 The Cosmic Computer (s) Piper, H. Beam (1976-2014)
12 Skylark Three (s) Smith, Edward E. (1979-2020)
12 The Skylark of Space (s) Smith, Edward E. (1979-2020)
12 Heirs of Empire (s) Weber, David (1996-2015)
12 Mutineers' Moon (s) Weber, David (1991-2015)
12 The Present (sr) Holbrook, Cindy (1996-2005)
11 Saving Grace (r) Garwood, Julie (1995-2004) ***
11 Lady of Quality (r) Heyer, Georgette (1993-2000) ***
11 The Black Moth (r) Heyer, Georgette (1993-2011) ***
11 Pepper's Way (r) Hooper, Kay (1997-2016) ****
11 A Woman's Touch (r) Krentz, Jayne Ann (1996-2013) ****
11 Day of the Giants (s) del Rey, Lester (1977-2017)
11 Tactics of Mistake (s) Dickson, Gordon R. (1975-2020)
11 The Flying Warlord (s) Frankowski, Leo (1989-2020)
11 The High-Tech Knight (s) Frankowski, Leo (1989-2020)
11 The Radiant Warrior (s) Frankowski, Leo (1989-2020)
11 Invader On My Back (s) High, Philip E. (1979-2015)
11 Twin Planets (s) High, Philip E. (1979-2021)
11 Dragonsinger (s) McCaffrey, Anne (1977-2008)
11 Dragonsong (s) McCaffrey, Anne (1976-2008)
11 Little Fuzzy (s) Piper, H. Beam (1976-2020)
11 Shock Wave (s) Richmond, Walt & Leigh (1975-2019)
11 The Armageddon Inheritance (s) Weber, David (1993-2015)
10 Amaryllis (r) Castle, Jayne (1996-2017) ***
10 Zinnia (r) Castle, Jayne (1997-2017) ***
10 For the Roses (r) Garwood, Julie (1996-2018) ***
10 Sylvester, or The Wicked Uncle (r) Heyer, Georgette (1993-2016) ****
10 The Masqueraders (r) Heyer, Georgette (1993-2001) ****
10 High Energy (r) Joy, Dara (1996-2020) *****
10 Minor Indiscretions (r) Metzger, Barbara (1993-2020) ****
10 The Primrose Path (r) Reece, Jean (1994-2020) *****
10 Four in Hand (r) Westhaven, Margaret (1994-2018) ***
10 The Varkaus Conspiracy (s) Dalmas, John (1983-2017)
10 Orphan Star (s) Foster, Alan Dean (1977-2002)
10 Lord Conrad's Lady (s) Frankowski, Leo (1990-2020)
10 The Genesis Machine (s) Hogan, James P. (1978-2019)
10 The Wailing Asteroid (s) Leinster, Murray (1978-2016)
10 Emergence (s) Palmer, David R. (1984-2018)
10 Space Viking (s) Piper, H. Beam (1976-2020)
10 The Anything Tree (s) Rackham, John (1978-2016)
10 The Beasts of Kohl (s) Rackham, John (1976-2003)
10 The Probability Corner (s) Richmond, Walt & Leigh (1977-2015)
10 Spacehounds of IPC (s) Smith, Edward E. (1981-2020)
9 The Wayward Heiress (r) Chenier, Blanche (1994-2010) ****
9 Faro's Daughter (r) Heyer, Georgette (1993-2016) ***
9 The Grand Sophy (r) Heyer, Georgette (1993-2015) ****
9 The Talisman Ring (r) Heyer, Georgette (1994-2016) ***
9 The Toll-Gate (r) Heyer, Georgette (1993-2015) ****
9 Family Man (r) Krentz, Jayne Ann (1996-2018) ***
9 Hidden Talents (r) Krentz, Jayne Ann (1996-2013) ***
9 Warrior's Woman (r) Lindsey, Johanna (1996-2010) **
9 Desire (r) Quick, Amanda (1995-2005) ***
9 Anton York, Immortal (s) Binder, Eando (1978-2017)
9 Wolfling (s) Dickson, Gordon R. (1979-2016)
9 Strings (s) Duncan, Dave (1990-2012)
9 1632 (s) Flint, Eric (2001-2009)
9 The Tar-Aiym Krang (s) Foster, Alan Dean (1978-2002)
9 Dragondrums (s) McCaffrey, Anne (1979-2002)
9 The Witches of Karres (s) Schmitz, James H. (1979-2013)
9 Galactic Patrol (s) Smith, Edward E. (1976-2017)
9 Gray Lensman (s) Smith, Edward E. (1976-2017)
9 Second Stage Lensmen (s) Smith, Edward E. (1976-2017)
8 Orchid (r) Castle, Jayne (1998-2017) ****
8 A Country Chit (r) Dalton, Emily (1994-2011) ***
8 Castles (r) Garwood, Julie (1995-2003) **
8 Guardian Angel (r) Garwood, Julie (1995-2003) ***
8 The Prize (r) Garwood, Julie (1995-2004) ***
8 A Scandalous Portrait (r) Hamilton, Violet (1994-1999) 0
8 False Colours (r) Heyer, Georgette (1993-2015) ***
8 Regency Buck (r) Heyer, Georgette (1993-2011) **.5
8 Sprig Muslin (r) Heyer, Georgette (1992-2016) ****
8 The Earl's Fancy (r) Hines, Charlotte (1995-2000) ****
8 Full Bloom (r) Krentz, Jayne Ann (1996-2008) ***
8 The Winter Picnic (r) McKeone, Dixie (1994-1998) ****
8 Lady in Green (r) Metzger, Barbara (1993-2020) ****
8 Reckless (r) Quick, Amanda (1995-2017) ***
8 The Duke's Mistress (r) Stewart, Lois (1994-1997) ***
8 The Practice Effect (s) Brin, David (1984-2015)
8 The Walkaway Clause (s) Dalmas, John (1986-2017)
8 Bloodhype (s) Foster, Alan Dean (1978-2002)
8 The End of the Matter (s) Foster, Alan Dean (1977-1997)
8 Citizen of the Galaxy (s) Heinlein, Robert A. (1979-2014)
8 The Moon is a Harsh Mistress (s) Heinlein, Robert A. (1977-2019)
8 The Number of the Beast (s) Heinlein, Robert A. (1980-2019)
8 Time Enough for Love (s) Heinlein, Robert A. (1976-2019)
8 The Pirates of Zan (s) Leinster, Murray (1978-2013)
8 Daughters of the Dolphin (s) Meyers, Roy (1977-2016)
8 Destiny and the Dolphins (s) Meyers, Roy (1977-2016)
8 Fuzzy Sapiens (s) Piper, H. Beam (1977-2020)
8 Children of the Lens (s) Smith, Edward E. (1978-2017)
8 Masters of the Vortex (s) Smith, Edward E. (1978-2017)
8 Ethical Quotient (ss) Phillifent, John T. (1980-2011)
7 The Earl and the Émigrée (r) Chater, Elizabeth (1994-1999) ***
7 The Runaway Debutante (r) Chater, Elizabeth (1995-1999) ***
7 A Heavenly Houseguest (r) Dalton, Emily (1994-2011) ****
7 Lady in Black (r) Dodd, Christina (1997-2009) ****
7 Rebellious Desire (r) Garwood, Julie (1995-2004) **
7 The Gift (r) Garwood, Julie (1995-2003) ***
7 The Nonesuch (r) Heyer, Georgette (1993-2015) ***
7 The Reluctant Widow (r) Heyer, Georgette (1993-2015) ****
7 Rebel Waltz (r) Hooper, Kay (1998-2012) ****
7 Perfect Partners (r) Krentz, Jayne Ann (1996-2017) ****
7 The Main Attraction (r) Krentz, Jayne Ann (1996-2002) ***
7 Daughters Four (r) McKeone, Dixie (1994-1998) ****
7 An Affair of Interest (r) Metzger, Barbara (1993-1997) ****
7 Father Christmas (r) Metzger, Barbara (1995-2019) ***
7 Patience Is a Virtue (r) Nelson, Judith (1996-2020) *****
7 The Merry Chase (r) Nelson, Judith (1996-2020) *****
7 Mischief (r) Quick, Amanda (1997-2004) ***
7 Surrender (r) Quick, Amanda (1995-2005) ***
7 The Duke's Design (r) Westhaven, Margaret (1994-1996) ***
7 A Planet of Your Own (s) Brunner, John (1977-2003)
7 The General's President (s) Dalmas, John (1988-2017)
7 The Reality Matrix (s) Dalmas, John (1986-2017)
7 The Scroll of Man (s) Dalmas, John (1985-2017)
7 The Coming of Wisdom (s) Duncan, Dave (1989-2012)
7 The Destiny of the Sword (s) Duncan, Dave (1989-2012)
7 The Reluctant Swordsman (s) Duncan, Dave (1989-2012)
7 Man of Many Minds (s) Evans, E. Everett (1978-2005)
7 To Sail Beyond the Sunset (s) Heinlein, Robert A. (1987-2019)
7 The Lark & the Wren (s) Lackey, Mercedes (1992-2018)
7 Four From Planet 5 (s) Leinster, Murray (1979-2013)
7 The Greks Bring Gifts (s) Leinster, Murray (1979-2013)
7 The White Dragon (s) McCaffrey, Anne (1978-2001)
7 Dolphin Boy (s) Meyers, Roy (1977-1997)
7 Threshold (s) Palmer, David R. (1985-2019)
7 Matadora (s) Perry, Steve (1987-1994)
7 The Proxima Project (s) Rackham, John (1975-2017)
7 Challenge the Hellmaker (s) Richmond, Walt & Leigh (1976-2002)
7 First Lensman (s) Smith, Edward E. (1978-2017)
7 Triplanetary (s) Smith, Edward E. (1978-2017)
7 The Warlock In Spite of Himself (s) Stasheff, Christopher (1977-1993)
7 Mairelon the Magician (s) Wrede, Patricia C. (1992-2018)
6 An Infamous Sea Bath (r) Dalton, Emily (1994-2011) ***
6 Cotillion (r) Heyer, Georgette (1993-2015) ****
6 The Convenient Marriage (r) Heyer, Georgette (1993-2015) ****
6 The Quiet Gentleman (r) Heyer, Georgette (1993-2004) ***
6 Deep Waters (r) Krentz, Jayne Ann (1997-2013) ***
6 Grand Passion (r) Krentz, Jayne Ann (1996-2008) ***
6 Wildest Hearts (r) Krentz, Jayne Ann (1996-2013) ***
6 An Angel for the Earl (r) Metzger, Barbara (1994-1996) ****
6 Invaders from the Infinite (s) Campbell, John W. (1977-2015)
6 Islands of Space (s) Campbell, John W. (1977-2015)
6 The Black Star Passes (s) Campbell, John W. (1977-2015)
6 Prison Planet (s) Dietz, William C. (1989-2002)
6 Flinx in Flux (s) Foster, Alan Dean (1988-2002)
6 Double Star (s) Heinlein, Robert A. (1980-1991)
6 Methuselah's Children (s) Heinlein, Robert A. (1976-2013)
6 Stranger in a Strange Land (s) Heinlein, Robert A. (1976-2013)
6 The Cat Who Walks Through Walls (s) Heinlein, Robert A. (1985-2019)
6 The Fairy Godmother (s) Lackey, Mercedes (2004-2020)
6 Plan B (s) Lee, Sharon & Miller, Steve (1999-2009)
6 Operation: Outer Space (s) Leinster, Murray (1979-2013)
6 Dragonflight (s) McCaffrey, Anne (1979-1997)
6 The Rowan (s) McCaffrey, Anne (1991-2016)
6 Dawn for a Distant Earth (s) Modesitt, L. E. Jr. (1987-2003)
6 The Ecologic Envoy (s) Modesitt, L. E. Jr. (1986-1997)
6 The Machiavelli Interface (s) Perry, Steve (1987-1994)
6 The Man Who Never Missed (s) Perry, Steve (1987-1994)
6 The Omega Cage (s) Perry, Steve & Reaves, Michael (1988-2002)
6 King of Argent (s) Phillifent, John T. (1982-2017)
6 Fuzzies and Other People (s) Piper, H. Beam (1984-2020)
6 Gallagher's Glacier (s) Richmond, Walt & Leigh (1975-1997)
6 Phase Two (s) Richmond, Walt & Leigh (1979-2002)
6 Call Him Dead (s) Russell, Eric Frank (1976-1997)
6 The Universe Against Her (s) Schmitz, James H. (1983-1997)
6 True Names (s) Vinge, Vernor (1983-1990)
6 Lord of Light (s) Zelazny, Roger (1976-2017)
6 Santa Reads Romance (sr) Joy, Dara (1997-2005) *****
6 The Lost Kafoozalum (ss) Ashwell, Pauline (1976-1991)
6 Unwillingly to School (ss) Ashwell, Pauline (1976-1991)
6 Prologue to . . . an Analogue (ss) Richmond, Walt & Leigh (1983-2020)
5 Asterix and the Goths (c) Goscinny, Rene & Uderzo, Albert (1975-1981)
5 Asterix and the Laurel Wreath (c) Goscinny, Rene & Uderzo, Albert (1975-1981)
5 Asterix the Gaul (c) Goscinny, Rene & Uderzo, Albert (1975-1981)
5 Escapade (r) Devon, Marian (1994-1999) ****
5 Gentle Warrior (r) Garwood, Julie (1995-2004) **
5 An Infamous Army (r) Heyer, Georgette (1993-2011) **.5
5 Lady Megan's Masquerade (r) Holbrook, Cindy (1995-1995) ****
5 On the First Day of Christmas (r) Holbrook, Cindy (1999-2009) ****
5 The Country Gentleman (r) Holbrook, Cindy (1997-2019) ****
5 The Reluctant Bride (r) Holbrook, Cindy (1998-2019) *****
5 Mackenzie's Mission (r) Howard, Linda (2000-2014) ***
5 Mackenzie's Mountain (r) Howard, Linda (2000-2014) ***
5 The Somerville Farce (r) Kasey, Michelle (1994-1998) ***
5 All Night Long (r) Krentz, Jayne Ann (2006-2013) ***.5
5 Crystal Flame (r) Krentz, Jayne Ann (1996-1999) **
5 Mutiny at Almack's (r) Lansdowne, Judith A. (1999-2014) *****
5 Devil's Bride (r) Laurens, Stephanie (2000-2009) ***
5 A Highly Respectable Widow (r) McRae, Melinda (1993-1997) 0
5 My Lady Innkeeper (r) Metzger, Barbara (1994-2000) ***
5 The Questioning Miss Quinton (r) Michaels, Kasey (1994-1998) ***
5 The Wagered Miss Winslow (r) Michaels, Kasey (1995-1995) ***
5 A Matchmaking Miss (r) Overfield, Joan (1995-1999) ***
5 The Lark's Nest (r) Pianka, Phyllis Taylor (1994-1998) ***
5 Lie by Moonlight (r) Quick, Amanda (2005-2016) ***.5
5 With This Ring (r) Quick, Amanda (1999-2006) ****.5
5 Monument (s) Biggle, Lloyd Jr. (1978-1997)
5 The Stardroppers (s) Brunner, John (1978-2016)
5 The Playmasters (s) Dalmas, John & Martin, Rod (1987-2017)
5 Lest Darkness Fall (s) de Camp, L. Sprague (1975-1990)
5 The Door Into Fire (s) Duane, Diane (1979-1990)
5 Harlot's Ruse (s) Friesner, Esther M. (1986-1992)
5 Tunnel in the Sky (s) Heinlein, Robert A. (1978-2017)
5 Hellspark (s) Kagan, Janet (1992-2016)
5 Mirabile (s) Kagan, Janet (1992-2016)
5 Lifter (s) Kilian, Crawford (1987-1997)
5 I Dare (s) Lee, Sharon & Miller, Steve (2002-2009)
5 Gateway to Elsewhere (s) Leinster, Murray (1976-2002)
5 The Forgotten Planet (s) Leinster, Murray (1979-2003)
5 Fire in the Mist (s) Lisle, Holly (1992-1997)
5 The Girl, The Gold Watch, & Everything (s) MacDonald, John D. (1979-1994)
5 Damia (s) McCaffrey, Anne (1993-2016)
5 Damia's Children (s) McCaffrey, Anne (1994-2016)
5 Dragonquest (s) McCaffrey, Anne (1979-1997)
5 Lyon's Pride (s) McCaffrey, Anne (1995-2016)
5 Pegasus in Flight (s) McCaffrey, Anne (1991-2016)
5 In Endless Twilight (s) Modesitt, L. E. Jr. (1988-2003)
5 The Silent Warrior (s) Modesitt, L. E. Jr. (1987-2003)
5 Cloud Chamber (s) Myers, Howard L. (1978-2017)
5 Instant Gold (s) O'Rourke, Frank (1976-1997)
5 The Albino Knife (s) Perry, Steve (1991-1994)
5 Four-Day Planet (s) Piper, H. Beam (1979-2002)
5 The Double Invaders (s) Rackham, John (1979-2009)
5 Time to Live (s) Rackham, John (1977-2009)
5 Space Pioneer (s) Reynolds, Mack (1978-1996)
5 Tomorrow Might be Different (s) Reynolds, Mack (1976-2009)
5 Grand Central Arena (s) Spoor, Ryk E. (2011-2020)
5 Noninterference (s) Turtledove, Harry (1988-2018)
5 The Blue World (s) Vance, Jack (1984-2015)
5 On Basilisk Station (s) Weber, David (1993-2001)
5 The Excalibur Alternative (s) Weber, David (2002-2015)
5 An Enemy of the State (s) Wilson, F. Paul (1980-2004)
5 This Immortal (s) Zelazny, Roger (1976-1991)
5 Bridal Jitters (sr) Castle, Jayne (1999-2020) **
5 Snake Eyes (ss) Foster, Alan Dean (1978-1990)
5 The Ambulance Made Two Trips (ss) Leinster, Murray (1976-1990)
5 Compulsion (ss) Schmitz, James H. (1977-2012)
5 Glory Day (ss) Schmitz, James H. (1977-2012)
A high percentage of the books I read are in series, so another way to identify my favorites is to look at series or universes in which I have read (and may still be reading) many books, even though many books in the series have not been read enough times to show in the list above. Below are a few favorite series.
The first 3 books in the Liaden Universe by Sharon Lee & Steve Miller are near the top of the list above, and 2 later books are lower in the list, but there have been a lot published since those that I haven't had time to reread as many times. The various stories & books have been released in so many overlapping chapbooks, collections, & other compilations over the years that I'm not sure of an exact unduplicated count of books, but it is well over 20.
The Curtain and Harmony books by Jayne Castle, several of which are in the list above.
Counting novels, Ring of Fire anthologies, and issues of the Grantville Gazette, I have read over 100 books in the 1632verse started by the novel 1632 by Eric Flint (which is in the list above).
The Dahak trilogy and several standalone novels by David Weber are in the list above, but only the first book in his Honorverse made the 5-readings cutoff. I consider all the books in that universe to be one series, though they are often listed as multiple separate series, so I count that series as over 20 mostly very long books. I am impatiently waiting for more. His War God series is great fantasy that I also want to see resolved.
All the books in both the Lensmen and the Skylark series, and a few standalone novels, by Edward E. Smith (E. E. “Doc” Smith) are in the list above. I keep reading his books despite realizing that they almost all include genocidal wars.
Many Anne McCaffrey books are in the list above, including several in the Pern and Pegasus/Tower & Hive series, and I have read many of her other books multiple times.
The whole Asterix series of graphic novels by Rene Goscinny & Albert Uderzo, a few of which are at the bottom of the list above. The wordplay is wonderful, which is especially impressive given that I read English translations. I understand that the French originals have as much wordplay. My siblings & I hunted these books for years decades ago, when they were pretty hard to find. Modern online sources make them a lot easier to find (but not cheaper).
Other series I have liked (and in several cases I am still getting new releases), with multiple books but few rereadings:
The Dragon Kin and related series by G. A. Aiken.
The Bewitched and Bewildered series by Alanea Alder.
The Magic (Kate Daniels & spin-offs), Inkeeper Chronicles, & Hidden Legacy series by Ilona Andrews.
The Myth series by Robert Asprin.
The Applied Topology series by Margaret Ball.
The Ministry of Peculiar Occurrences series by Pip Ballantine & Tee Morris.
Several paranormal romance series by Dana Marie Bell.
The Others and related series by Anne Bishop.
The Darkover series by Marion Zimmer Bradley.
The Mercy Thompson and Alpha & Omega series by Patricia Briggs.
The Guardians and Iron Seas series by Meljean Brook.
The Vlad Taltos series by Steven Brust, though I am 8 books behind in reading these.
The Vorkosigan and Five Gods series by Lois McMaster Bujold.
Several series by Lindsay Buroker.
The Parasol Protectorate and related series by Gail Carriger.
The Cassie Palmer and related series by Karen Chance.
The Sten series by Allan Cole & Chris Bunch.
The Dragon Blood and other series by Lindsay Buroker.
The Immortals After Dark series by Kresley Cole.
The Wizardry series by Rick Cook.
The Regiment and Yngling series by John Dalmas.
The Childe Cycle by Gordon R. Dickson.
The Class 5 series by Michelle Diener.
The Immortal Guardians and related series by Dianne Duvall.
The Heirs of Alexandria series by Eric Flint & Dave Freer & Mercedes Lackey.
The Humanx Commonwealth and related series by Alan Dean Foster (some books listed above).
The Conrad Stargard series by Leo Frankowski (first 5 books listed above).
The Night Huntress and related series by Jeaniene Frost.
The Pandora and WarSpell series by Paula Goodlett & Gorg Huff.
The Hollows (Rachel Morgan) series by Kim Harrison.
The Elder Races series by Thea Harrison.
The Iron Druid series by Kevin Hearne (though I didn't like the ending).
The Tala and related series by Jeffe Kennedy.
The Dark-Hunter series by Sherrilyn Kenyon, though this is qualified, and I still haven't read the last 9 books in the series.
The Insignia trilogy by S. J. Kincaid
The Mageverse and related series by Angela Knight.
The Arcane Society series by JAK (Jayne Castle / Jayne Ann Krentz / Amanda Quick).
Several series by Mercedes Lackey.
The Cynster and related series by Stephanie Laurens.
The Pack and Pride and related series by Shelly Laurenston.
The Ancillary trilogy by Ann Leckie.
The London Steampunk and related series by Bec McMaster.
The WebMage series by Kelly McCullough.
The Known Space series by Larry Niven.
The first books of the Temeraire series by Naomi Novik (I've only read the first four so far).
The Celta series by Robin D. Owens.
The Matador series by Steve Perry.
Several fantasy series by Tamora Pierce.
Several Paratime and Federation stories by H. Beam Piper beyond those listed above.
Several romance series by Penny Reid.
The Esther Diamond series by Laura Resnick.
The Ganymede Survivors and Human Diaspora series by Val Roberts.
The Callahan series by Spider Robinson.
The Harry Potter series by J. K. Rowling.
The Argeneau Vampire series by Lynsay Sands.
The Old Man's War series by John Scalzi.
The Kensho series by Dennis Schmidt.
The Hub series by James H. Schmitz, a few of which are in the list above.
The Karres series by James H. Schmitz and several posthumous collaborators.
The Raine Benares and SPI Files series by Lisa Shearin.
The Psy-Changelings series by Nalini Singh.
The Love at Stake series by Kerrelyn Sparks.
The Ukiah Oregon and Elfhome series by Wen Spencer.
The Warlock and related series by Christopher Stasheff, the first of which is listed above.
The Enchanted, Inc. (Katie Chandler) and Fairy Tale series by Shanna Swendson.
The Lady Sherlock mysteries by Sherry Thomas.
The Others and Gargoyles series by Christine Warren.
The Ethshar series by Lawrence Watt-Evans.
The Sector General series by James White.
The Lupi series by Eileen Wilks. One final announced as planned book has yet to be published.
The LaNague Federation series by F. Paul Wilson.
The Enchanted Forest and Mairelon series by Patricia C. Wrede.
The Cecelia & Kate series by Patricia C. Wrede & Caroline Stevermer.
One final way to show my favorites is by author. Below is a list of separate book counts and total readings counts, in a descending sort by readings (cutting off at 10 readings). Genre codes are the same as with the first list above, adding (c) for Comics or Humor, (ssr) for Short Standalone Romance, and (sss) for Short Standalone F&SF. Since Jayne Ann Krentz, Amanda Quick, Jayne Castle, and Stephanie James are all names used by one author, JAK is actually the author I have read the most books by the most times, with 492 readings of 156 books.
Books Readings (Genre) Author
35 277 (r) Heyer, Georgette
75 225 (r) Krentz, Jayne Ann
37 193 (r) Quick, Amanda
34 185 (r) Garwood, Julie
44 160 (s) McCaffrey, Anne
16 157 (s) Smith, Edward E.
42 144 (r) Metzger, Barbara
44 134 (s) Lee, Sharon & Miller, Steve
32 127 (s) Weber, David
56 122 (s) Foster, Alan Dean
33 110 (s) Heinlein, Robert A.
38 109 (s) Leinster, Murray
65 105 (r) Michaels, Kasey
15 96 (r) Holbrook, Cindy
14 84 (s) Piper, H. Beam
52 83 (s) Norton, Andre
17 83 (s) High, Philip E.
27 80 (s) Dalmas, John
35 72 (c) Goscinny, Rene & Uderzo, Albert
26 72 (s) Brunner, John
8 60 (s) Frankowski, Leo
56 58 (r) Smith, Joan
30 58 (s) Dickson, Gordon R.
49 52 (r) Leclaire, Day
20 52 (s) Duncan, Dave
45 50 (r) Laurens, Stephanie
27 50 (s) Stasheff, Christopher
14 50 (r) Darcy, Clare
48 49 (s) Anthony, Piers
9 49 (s) Richmond, Walt & Leigh
41 48 (r) MacAlister, Katie
21 48 (s) Modesitt, L. E. Jr.
35 47 (s) Lackey, Mercedes
46 46 (s) Goodlett, Paula ed.
17 46 (r) Castle, Jayne
32 45 (r) Mansfield, Elizabeth
15 45 (s) Schmitz, James H.
44 44 (r) Christenberry, Judy
43 43 (r) Shalvis, Jill
9 43 (s) Rackham, John
34 41 (s) Bujold, Lois McMaster
21 41 (r) Hooper, Kay
40 40 (r) Sands, Lynsay
39 39 (s) Appleton, Victor
38 38 (r) Langlais, Eve
27 38 (r) Lindsey, Johanna
25 38 (s) Laumer, Keith
21 37 (r) Howard, Linda
20 37 (r) Chater, Elizabeth
36 36 (r) Alexander, Victoria
32 36 (r) Jeffries, Sabrina
23 36 (s) Zelazny, Roger
20 36 (r) Lansdowne, Judith A.
22 35 (r) Devon, Marian
19 35 (r) Laurenston, Shelly
28 34 (s) Farmer, Philip Jose
23 34 (r) Dunn, Carola
21 34 (s) Reynolds, Mack
12 34 (r) Dalton, Emily
11 34 (s) Perry, Steve
9 34 (r) Nelson, Judith
33 33 (s) Boyes, Walt & Hasseler, Bjorn ed.
29 33 (s) Pierce, Tamora
13 33 (r) Westhaven, Margaret
31 32 (r) Holly, Emma
16 32 (r) Crusie, Jennifer
31 31 (r) Bell, Dana Marie
31 31 (s) Buroker, Lindsay
28 31 (r) Quinn, Julia
27 31 (s) Watt-Evans, Lawrence
9 31 (r) Martin, Michelle
30 30 (r) Monroe, Max
29 30 (r) Davidson, MaryJanice
28 30 (r) Thompson, Vicki Lewis
29 29 (r) Fenske, Tawna
28 29 (r) Beverley, Jo
23 29 (r) Chase, Loretta
14 29 (s) McIntosh, J. T.
7 29 (s) Wilson, F. Paul
28 28 (r) Warren, Christine
27 28 (r) James, Stephanie
25 28 (r) Kelly, Carla
22 28 (s) Turtledove, Harry
23 27 (r) McWilliams, Judith
22 27 (s) de Camp, L. Sprague
10 26 (s) Campbell, John W.
24 25 (s) Andrews, Ilona
21 25 (s) Cherryh, C. J.
12 25 (s) Hogan, James P.
12 25 (s) Wrede, Patricia C.
24 24 (s) Galenorn, Yasmine
23 24 (r) Long, Julie Anne
23 24 (s) Chalker, Jack L.
22 24 (r) Knight, Angela
19 24 (r) Sebastian, Margaret
15 24 (s) Fox, Gardner F.
14 24 (s) Spoor, Ryk E.
23 23 (r) Jacobs, Holly
10 23 (r) Evanovich, Janet
3 23 (s) Meyers, Roy
22 22 (r) Arend, Vivian
22 22 (r) Reid, Penny
22 22 (s) Blaine, John
22 22 (s) Briggs, Patricia
21 22 (r) Gracie, Anne
18 22 (s) Friesner, Esther M.
18 22 (s) Simak, Clifford D.
18 22 (s) White, James
7 22 (r) Joy, Dara
21 21 (r) Gibson, Rachel
21 21 (r) Kenyon, Sherrilyn
21 21 (s) Clayton, Jo
16 21 (r) Brockway, Connie
14 21 (s) Brust, Steven
14 21 (s) Morressy, John
13 21 (r) Peters, Clarice
10 21 (s) Binder, Eando
1 21 (s) Smith, Edward E. & Evans, E. E.
20 20 (r) Goodman, Jo
20 20 (s) Ball, Margaret
15 20 (r) Carroll, Susan
13 20 (s) Spencer, Wen
19 19 (r) Bailey, Tessa
19 19 (r) D'Alessandro, Jacquie
19 19 (r) McCarthy, Erin
19 19 (r) Owens, Robin D.
19 19 (r) Singh, Nalini
19 19 (s) Chance, Karen
19 19 (s) Harrison, Kim
18 19 (r) Phillips, Susan Elizabeth
17 19 (s) Hughes, Zach
14 19 (s) Busby, F. M.
11 19 (s) Leiber, Fritz
9 19 (r) Pianka, Phyllis Taylor
9 19 (s) Brin, David
6 19 (r) McKeone, Dixie
4 19 (s) Palmer, David R.
18 18 (r) MacKeever, Maggie
16 18 (s) Asprin, Robert
15 18 (s) Robinson, Spider
14 18 (s) Tepper, Sheri S.
10 18 (r) Wynn, Patricia
7 18 (s) Schmidt, Dennis
17 17 (r) Bangs, Nina
17 17 (r) Grant, Pippa
17 17 (r) Simmons, Deborah
17 17 (r) Sparks, Kerrelyn
17 17 (s) Carriger, Gail
16 17 (c) Davis, Jim
16 17 (c) Walker, Mort
13 17 (s) Niven, Larry
13 17 (s) van Vogt, A. E.
11 17 (s) Sheffield, Charles
5 17 (s) Vance, Jack
3 17 (s) Cristabel
1 17 (s) Piper, H. Beam & McGuire, John J.
16 16 (r) Allen, Louise
16 16 (r) Cole, Kresley
16 16 (s) Swendson, Shanna
8 16 (s) Flint, Eric
7 16 (r) Chenier, Blanche
6 16 (r) Kasey, Michelle
4 16 (r) Damon, Lee
15 15 (m) Harris, Charlaine
15 15 (r) Cach, Lisa
15 15 (r) Lau, Jackie
15 15 (r) Warren, Nancy
15 15 (s) Flint, Eric ed.
15 15 (s) Frost, Jeaniene
15 15 (s) Shearin, Lisa
15 15 (ssr) Bell, Dana Marie
13 15 (r) Enoch, Suzanne
13 15 (r) Saunders, Irene
12 15 (r) Williams, Claudette
8 15 (s) Dietz, William C.
7 15 (s) Russell, Eric Frank
5 15 (s) del Rey, Lester
5 15 (s) McCullough, Kelly
2 15 (r) Lynson, Jane
14 14 (r) Brook, Meljean
14 14 (r) Duvall, Dianne
14 14 (r) Kennedy, Jeffe
14 14 (s) Pratchett, Terry
14 14 (s) Wilks, Eileen
13 14 (r) Hill, Sandra
13 14 (r) Wolf, Joan
12 14 (s) Jones, Diana Wynne
12 14 (s) Shaw, Bob
11 14 (c) Browne, Dik
11 14 (r) Diener, Michelle
11 14 (r) Hocker, Karla
11 14 (s) de Chancie, John
10 14 (s) Cowper, Richard
8 14 (r) Dodd, Christina
8 14 (r) Roberts, Val
13 13 (r) Alder, Alanea
13 13 (r) Kendall, Karen
13 13 (r) King, Valerie
13 13 (r) Kleypas, Lisa
13 13 (r) Nicholas, Erin
13 13 (s) Alexander, Lloyd
13 13 (s) Anderson, Poul
13 13 (s) Caine, Rachel
13 13 (s) Hearne, Kevin
13 13 (ssr) Knight, Angela
12 13 (r) Aiken, G. A.
12 13 (r) Calvin, June
11 13 (r) Jensen, Emma
10 13 (s) Sohl, Jerry
9 13 (r) Overfield, Joan
6 13 (r) Hamilton, Violet
6 13 (r) Stewart, Lois
12 12 (r) Blakely, Lauren
12 12 (r) Clayton, Alice
12 12 (r) D'Arc, Bianca
12 12 (r) Dade, Olivia
12 12 (r) Frame, Mary
12 12 (r) Harrison, Thea
12 12 (r) McMaster, Bec
12 12 (s) Bradley, Marion Zimmer
12 12 (ssr) Harrison, Thea
10 12 (r) Smythe, Sheridon
10 12 (s) van Scyoc, Sydney
9 12 (s) Pournelle, Jerry
8 12 (r) McRae, Melinda
7 12 (s) Kilian, Crawford
7 12 (s) Smith, George O.
7 12 (s) Vinge, Vernor
5 12 (s) Mason, David
4 12 (s) Phillifent, John T.
3 12 (s) Evans, E. Everett
11 11 (r) Carmichael, Jeanne
11 11 (r) Chesney, Marion
11 11 (r) Coulter, Catherine
11 11 (r) Heath, Sandra
11 11 (r) Huntington, Kate
11 11 (r) Rutland, Eva
11 11 (r) Simpson, Donna
11 11 (s) Goldin, Stephen
11 11 (s) Jakes, John
11 11 (s) Smith, L. Neil
11 11 (sss) Andrews, Ilona
10 11 (r) Barnett, Jill
10 11 (s) Carver, Jeffrey A.
10 11 (s) Zahn, Timothy
9 11 (r) Farr, Diane
8 11 (s) Dickinson, Peter
7 11 (s) Duane, Diane
4 11 (r) Hines, Charlotte
3 11 (s) Kagan, Janet
2 11 (r) Reece, Jean
10 10 (c) Hooker & Butterworth
10 10 (r) Black, Jaid
10 10 (r) Cabot, Meg
10 10 (r) Callihan, Kristen
10 10 (r) Hern, Candice
10 10 (r) James, Eloisa
10 10 (r) Kenner, Julie
10 10 (r) Krahn, Betina
10 10 (r) Mars, Diana
10 10 (r) Martin, Annika
10 10 (r) Pape, Cindy Spencer
10 10 (r) Sey, Susan
10 10 (r) Stacey, Shannon
10 10 (r) Stuart, Anne
10 10 (r) Summerville, Margaret
10 10 (r) Walsh, Sheila
10 10 (s) Goulart, Ron
10 10 (s) Silverberg, Robert
9 10 (r) Blair, Annette
9 10 (r) James, Julie
9 10 (r) Kistler, Julie
9 10 (s) Huff, Gorg & Goodlett, Paula
8 10 (r) Rabe, Sheila
8 10 (s) Blish, James
8 10 (s) Cole, Allan & Bunch, Chris
7 10 (s) Felice, Cynthia
5 10 (s) Lisle, Holly
4 10 (s) White, Ted
All the numbers above are based on my reading log, so they don't reflect anything I read before I started the log in 1975 when I was 20. I don't trust my memory enough to try to reconstruct my pre-log reading, though I'm sure I read The Swiss Family Robinson by Johann Wyss several times before the 3 readings in the log. I view it as an SF book, given the impossible island it is set on (with flora & fauna from all continents).
Finally, after three different ways of getting favorites from logged data, I will mention a few favorites simply based on current thoughts.
I first read a romance by Pippa Grant in late 2018, but she is now an auto-buy and read ASAP author for me. Her humor works for me—all but one of her books has enough humor for me to recommend for readers who want romances with humor.
I've enjoyed all the romances by Lucy Parker, but there have only been five so far.
I just started reading books by Erin Nicholas a couple years ago and still haven't read a lot of her back-list, but I've liked most the ones I've read.
I just started reading the fantasies of T. Kingfisher last year, and still haven't read her whole back-list, but I've liked all the ones I've read.
David R. Palmer had a couple books come out in the 1980s, both of which are in the reread list above. Their sequels finally came out decades later. Threshold (1985) is over-the-top in a way I enjoy, and Special Education (2019) is a great sequel.
Grand Central Arena by Ryk E. Spoor is recent enough that it just made the list above, and I've read the two available sequels, and I am very impatiently awaiting the next. This series definitely captures the (Gosh! Wow! BIG IDEAS!!) sense of wonder of some of the SF I grew up reading, and I highly recommend it. It includes a lot of homages, though the main one I noticed is having a major character named after a character in Doc Smith's Skylark series. This series is amazing! His Balanced Sword trilogy is also excellent fantasy with the feeling of a role-playing game universe, and several of his other books are set in various parts of that universe.