The Xanath Series by Piers Anthony

 1. A Spell for Chameleon
 2. The Source of Magic
 3. Castle Roogna
 4. Centaur Aisle
 5. Ogre, Ogre
 6. Night Mare
 7. Dragon on a Pedestal
 8. Crewel Lye : A Caustic Yarn
 9. Golem in the Gears
10. Vale of the Vole
11. Heaven Cent
12. Man from Mundania
13. Isle of View
14. Question Quest
15. The Color of Her Panties
16. Demons Don't Dream
17. Harpy Thyme
18. Geis of the Gargoyle
19. Roc and a Hard Place
20. Yon Ill Wind
21. Faun & Games
22. Zombie Lover
23. Xone of Contention
24. The Dastard