To the people suggesting fiction books...
Can you explain how this will help the original poster expand his knowledge? This is what he was asking for...
You'll learn a lot reading great fiction books. If nothing else, you'll learn how to write well. People who don't read good books are as rule terrible at writing. That makes them look stupid even when they aren't. Many of my engineer colleagues suffer from this. The OP was probably looking for non-fiction tips, but he'll be a better person if he reads some good fiction as well.
@Hygro: if you don't think many fiction books are "must-read", you probably haven't read very good books. My opinion is the opposite of yours: you can learn anything you need that is on non-fiction books from secondary sources, internet articles, etc. There is no secondary source for the experience that is reading "Crime and Punishment".