My favorite book of all time has to be Catch-22 by Joseph Heller. Its funny and clever and poignant the characters are all wonderfully described. The situations are so realistic the description of the military machine as a lumbering beast riddled all sorts of characters, the horror and the futility of existence contrasted with friendship and enterprise. Its just a great read cover to cover, I highly recommend it especially if you like to play with language Heller is a master of paradox and satire.
I never realised until today (yes I know I can be terribly out of touch) but he actually wrote a sequel to Catch-22 called Closing Time which I am now in the process of reading.