I really like reference books and this person at Powell's Blog has some nice ones to consider. I can't recommend any quite as cool or useful as she does, but here are a few worth considering. The Dictionary of Imaginary Places is a list of over 1,200 created places. It's fun to read and a great way to find new books. Penguin has some small atlases of World History which are great. Most history is taught with limited geographical context. With the atlases you can see what was happening in India at the same time as China and Europe. It will also help you better understand the relationships between countries, as in how the nations surrounding Rome helped collapse it. And the books are cheap. They also have a series of more specialized books. You can be way cooler if you start using lingo from Straight From the Fridge Dad. Sure most people will think you are chump for talking like a 30s gangster, but your friends will think it's a gas. While they laugh at you.