Personally I prefer non-fiction. With that in mind, I recommend the following.
The Making of the Atomic Bomb by
Richard Rhodes
Extremely well written history of this herculean effort by the Allies in World War Two. This book deservedly won the Pulitzer Prize.
The Civil War trilogy by
Shelby Foote
Probably the best written, most enjoyable, comprehensive and altogether enjoyable history of the American Civil War. Foote has a beautiful style and you really get drawn into this amazing story.
An Anatomy of Thought - The Origin and Machinery of the Mind by
Ian Glynn
One of the best introductions to the human brain, conciousness and neurology. Very readable, very interesting and very well written.
On the fiction side, I recommend
The Life of Pi by
Yann Martel
Recent Booker Prize winner and a very deserving one at that. Uplifting, fantastic story on the physical and spiritual journey of a ship-wreck survivor as he floats across the ocean on a life-raft... alone except for a tiger for company...
Catch 22 by
Joeseph Hellar
The best satirical anti-war novel you are ever likely to read. Laugh out loud funny, whimsical, passionate, heart-breaking, thought provoking. A true 20th century masterpiece.
I could go on, but that's enough to keep you busy for some time!
Mr Mephisto