Best book I have ever read: Catch-22 by Joseph Heller
Another favourite: The World According to Garp by John Irving
Surprised at their absence on the topic. Catch-22 is one of those books I forced myself to read slowly because I loved every word of it. It was a rich and wonderful experience, very few books have that effect on me these days.
Also, I recently read The Hitchiker's Guide to the Galaxy series and I hold it in high regard.