What are your favorite fiction novels that pertain to spirituality, the new age, or ancient civilizations?
I love the themes of reality and identity that Philip K. willy put into many of his books. "Ubik" is one that comes to mind.
Ubik is good, along with Do Androids Dream of Electric Sheep? from Philip willy.
Stranger in a Strange Land, by Robert Heinlein.
Don't really care for his other stuff, but Sati by Christopher Pike is wonderful. If you can get past their dollar bookstore thriller title, his The Last Vampire series is great- full of Hindu stories and allegories, and some stuff inspired by the 60's new age movement.
The Glass Bead Game, Narcissus and Goldmund, Demian, and of course Siddhartha, by Herman Hesse, although you might find the first overly pedantic.
Hope that was helpful!
The Chronicles of Narnia by CS Lewis.
Xanth series, by Piers Anthony