My list lines up with a lot of books that people have recommended here, so I'll try to add a few favorites that haven't been mentioned so far.
Fiction:
1. Ubik - I read a bunch of Philip K. Dick this year, but this was my favorite. It's delightfully mind bending and left me thinking about it long after the book was done.
2. All the Pretty Horses - Beautifully written. McCarthy has an uncanny ability to paint with words.
3. Cannery Row - Short, witty, and full of interesting characters.
Nonfiction:
1. The Idea Factory - A dive into how Bell Labs became such an innovation powerhouse and gives a rounded picture of the figureheads that brought it so much fame.
2. Moonwalking with Einstein - A fun read about a journalist who took researching a memory competition a bit too seriously.
3. Countdown to Zero Day - A fascinating look at the development and deployment of Stuxnet -- the virus built to set Iran's nuclear program back.