Over on Society of Torch, Pole and Rope, there's an inspirational reading cited which is among my favorites - Empire of the East by Fred Saberhagen.
I picked up this book when I was thirteen or fourteen, totally on a whim, and it really snapped me out of my Tolkien fixation (Moorcock was a few years off - probably the final nail in that particular coffin). It is still one of my favorites - one I go back to every few years. I liked the Books of Swords too - in fact one of my earliest attempts to create a game from scratch was based on the Twelve Swords - and even appreciated some of the books of Lost Swords.
Saberhagen's treatment of demons and wizardry here is one of my favorite takes - the messenger that restores the crippled Chup, who came to him with the sound of the wind blowing through dry leaves (if I remember correctly...) - the malicious bastard in the depths of the Blue Temple - I could go on and on. Great stuff. The wizard called Wood, and one of my absolute favorite characters/figures in fiction: the Emperor of the Swords books. What a foil!
I've looked at Saberhagen's web page, but found little elucidation or further exploration of that 'setting'. I am sure that his writing has influenced all of the fantasy gaming that I have run.