Oh, my. I have to pick just ten? Goodness... I have enough books in my apartment that I worry sometimes whether or not the floor will stand up under the weight of them. (Anybody a fan of the anime series Read or Die? Uh, yeah. That's me... )
Here is a random sampling of 10 books from my religion/philosophy library:
A History of God, Karen Armstrong
Atheist Universe, Mills & Sagan
The Demon-Haunted World, Carl Sagan
The Iliad, Homer
The Book of Chuang Tzu
Prometheus Rising, Robert Anton Wilson
The Second Sex, Simone de Beauvoir
Breaking the Spell, Daniel Dennett
I Sold my Soul on eBay, Hemant Mehta
American Gospel, John Meacham
That, of course, doesn't begin to touch on the broad range of religious texts on the shelves - the various Bible versions, the Qur'an, the Tibetan Book of the Dead, the Tao Te Ching, stuff about paganism, the works of Plato, the endless volumes of Greek mythology...