My favorite book ever is Zen and the Art of Motorcycle Maintenance. It has nothing to do with Motorcycle Maintenance and everything to do with Zen, QUALITY, life, the meaning of everything... every time I read it my soul grows. It's amazing. (Note: I majored in English and I highly recommend any other English or Philosophy major read this if you haven't already.)
Same goes for *anything* by Ralph Waldo Emerson and other transcendentalists involved in early American literature. I like Ben Franklin's stuff on Deism and Thomas Paine's "Common Sense" - that pamphlet change the political landscape of our country and it's *amazing* how the words STILL apply today!
Someone mentioned The Importance of Being Earnest - LOVE everything by Oscar Wilde!! Love any Jane Austin as well.
My favorite books for *entertainment* are all of the books by Phillipa Gregory (The Virgin's Lover, The Other Boleyn Girl, etc) pertaining to King Henry VIII and his various wives... love historical fiction.
I also dig all the Vampire Chronicals by Anne Rice and the Twilight Series kept me amused. And Jenna Jameson's autobiography was pretty entertaining also. Oh and I Hope They Serve Beer in Hell by Tucker Max... I read a chapter aloud to my boyfriend everynight before bed and we almost freaking died we laughed so hard.
I could keep going: Memoirs of a Geisha, Room With a View, Brave New World, 1984, Midnight in the Garden of Good and Evil,... all fun and good for the soul