Ahmed, Saladin 18
Alexander, Lloyd 25 - Skipping an upvote day because I was reminded of Taran Wanderer, a dreary slog in an otherwise quick-paced and enjoyable series. I suppose every big series has to have a "bad" book; The Silver Chair, A Dance with Dragons, Books 8 through... what, 10 of Wheel of Time? At least Brooks got his out of the way first.
Anthony, Piers 12
Augusta, Lady Gregory 20
Bear, Elizabeth 20
Brooks, Terry 20 - I loved the Heritage of Shannara series; especially the middle two books (Druid & Elf Queen), which were both more horror than they were fantasy (but in very different ways from each other!). If the derivative-ness of Sword of Shannara turned you off give some of his later stuff a read; Elfstones is great and Wishsong is highly underrated.
Bulfinch, Thomas 23
Cook, Glen 28
Froud, Brian & Alan Lee 21
Hickman, Tracy & Margaret Weis 7
Hodgson, William Hope 18
Jemisin, N.K. 21
Jordan, Robert 19
Kay, Guy Gavriel 21
LeGuin, Ursula 25
Lynch, Scott 22
McKillip, Patricia 22
Mieville, China 14
Peake, Mervyn 21
Pratchett, Terry 24
Sanderson, Brandon 26
Smith, Clark Ashton 21
Tolstoy, Nikolai 8 - Another couple of downvotes for a racist
Wolfe, Gene 22