What kind of books are you looking for? Religious? Spiritual? Drug related, tying into the above? Aliens? Atheist? Philosophical? Science?
Off of the top of my head, a few authors and notable books:
-Aldous Huxley - Brave New World(actually fiction, but if you get the one with Brave New World Revisited, he talks about the book, comparing it to society at that time. Also, these kinds of books are meant to reflect into the real world, giving you a new perspective, new ideas on what's going on.)
-Aldous Huxley - The Doors of Perception and Heaven and Hell(both are recalling experiences he has had with mescaline and other drugs. If you haven't read these, then you need to, seriously.)
He also has other stuff, if you're interested. Ape and Essence is good, and I'm sure if you look him up on Wikipedia, you'd be able to find some other things you're interested in.
-Daniel Pinchbeck - Breaking Open the Head(this is a book about modern shamanism. Talks about psychedelics, meditation, etc. I haven't read it, but I watched a documentary with him in it, and he seemed to be an eloquent speaker. I'm sure the book is well written.)
-Tom Wolfe - The Electic Kool-Aid Acid Test(nonfiction, follows a band in the 60s - it's about hippies and drugs)
-Rick Strassman - DMT: The Spirit Molecule(great book. The documentary version is great as well)
-Rick Strassman and company - Inner Paths to Outer Space(this talks about his DMT trials, mushrooms, aliens, and has sets of amazing drawings, paintings, and graphic art depicting people's descriptions of what they see on psychedelics)
Other notable books/authors that I haven't read, but should be good, are:
-Terence McKenna's Food of the Gods(postulates that Psilocybe mushrooms were the catalyst to human intelligence and creativity -- based on theories of how humans spread throughout the planet, and his own theories based on, in part, things he tripped about, and also cave paintings, written works, etc.)
-Timothy Leary's stuff
-Acid Dreams(can't remember the author)
Carl Sagan wrote a ton of stuff, some about the universe and metaphysics, and some about society. Pale Blue Dot, Cosmos, Contact, The Demon-Haunted World, etc. All very good books.
If you're into atheism, or want to look at religion at a different perspective in general, Daniel Dennett's Breaking the Spell is good. I did a speech on it in sociology while in high school.
Aside from those kinds of books, I mostly like fantasy based in mythology. The Alchemyst, American Gods, etc. When I was younger, I read mostly things like Harry Potter, Eragon, Incarnations of Immortality, that kind of thing.