Seconding both Wheel of Time and Foucault's Pendulum! I was also particularly fond of Baudalino. Some others of my favorites (I read a LOT):
Charles de Lint: various newford stories and novels. Start with Dreams Underfoot which blurs the line between a short story collection and a novel and then read Onion Girl. Urban fantasy/folklore/borderline soap opera stuff, and amazing. Knowing a bit about Celtic music, folklore and Native American spirituality will help, but isn't necessary (and you WILL by the end!)
Clive Barker's "Mr. B Gone". Really any of his books (Weaveworld and The Great and Secret Show are standouts), but Mr. B has an interesting take on metafiction, 4th wall and post-modern horror. Speaking of:
Mark Danielewski "House of Leaves". Brilliant book. Creepy, hypnotic, confusing and aware of the medium.
Neal Stephenson: anything by. "Snowcrash" is fun cyberpunk fare. "The Baroque Cycle" is historical fiction about Isaac Newton, banking and calculus. With pirates. His recent "Anathem" is about an alternate world monestary. He's got a wonderful, casual, hip and witty style that should be inappropriate for what he writes, but somehow it works.
Salaman Rushdie: "the Ground Beneath Her Feet". Dense symbolist magical realisim. All his books are good, but this is my favorite (possibly because as a musician I connected most with it).
Again, I read a lot, so if you want more recommendations, let me know. I do gravitate towards horror, fantasy and sci-fi, but not exclusively. Everything is worth reading at least once!
addendum: don't overlook something because you've already seen the movie. comparing and contrasting different adaptations is something that will help you when it comes to screenplays.