Ok, admittedly this is completely my personal opinion and based entirely on my taste in literature – so you have been warned.
- The Black Company Series by Glen Cook. Hands down the earlier books in the series are my favorite reads of all time.
- The Malazan Book of the Fallen Series by Steven Erikson. Along with the Novels of Malazan Empireby Ian C. Esslemont. The scale of the books is immense but it still made me care about individual characters.
- The Horseclans Series by Robert Adams. The way he handled the alternate history to create the world of the Horseclans was an interesting read.
- Alex Verus Series by Benedict Jacka. The way the modern day magician is handled so well and the characters are not good or bad necessarily, they are just real people.
- Sandman Slim Series by Richard Kadrey. It is irreverent, inappropriate, extremely entertaining modern fantasy noir with a twist.
- The Eternal Champion Books by Michael Moorcock. Elric of Melnibone, Jerry Cornelius, Corum, Dorian Hawkmoon, Erekose, and many others. Hard to go wrong with a Michael Moorcock book but the interrelated Eternal Champion books are my favorites.
- Garrett, P.I. Series by Glen Cook (again). Private eye noir in a fantasy setting, what’s not to love. Cook’s writing style keeps it from becoming too fantasy, he maintains a dose of gritty realism that pulls it off wonderfully.
- The Dresden Files by Jim Butcher. The writing style is very entertaining and the characters are interesting and fleshed out wonderfully.
From there it falls into a lot of fun to read series, Monster Hunter International Series by Larry Correia (with new Monster Hunter Memoirs by John Ringo), Berserker Series by Fred Saberhagen, Dune Series by Frank Herbert, the Chronicles of Thomas Covenant the Unbeliever by Stephen R. Donaldson, the Gentlemen Bastards by Scott Lynch, the Belgariad and Elenium Series by David Eddings, all of the Discworld books by Terry Pratchett, the King’s Blades by David Duncan, Tanith Lee’s Flat Earth books, Vlad Taltos Series by Steven Brust, Eddie LaCrosse Series by Alex Bledsoe, the Odd Thomas and Frankenstein Series by Dean Koontz, Phillip Jose Farmer’s World of Tiers and Riverworld Series, Wild Cards edited by George R.R. Martin, Myth-Adventures by Robert Asprin, the Thieve’s World Series edited by Robert Lynn Asprin and Lynn Abbey, and more..
I could go on and on and on but no one wants that.
Let me know your favorite book series, the one that has you always waiting for the next book and going back and rereading.