My best recommendations (off the top of my head)
The Old Man and the Sea by Ernest Hemingway (Short but powerful, Man and nature, some of the best ink ever put to paper)
A Song of Ice and Fire series by George R. R. Martin (For my money, the best fantasy series ever written)
Cosmos by Carl Sagan (Still the best popular science book, can change the way you look at the world around you and the sky above you)
Crime and Punishment by Fyodor Dostoevsky (Seems like it would be bore, but it is a riveting study of morality and tense thriller)
The Life of Pi by Yann Martel (In the same vein as Old Man and the Sea, just a great modern fable)