One of my Polish coworkers has gotten me interested in the country. A friend loaned me Adam Zamoyski's "Poland: A History," which was interesting but very very short. I'm looking for some good books in English that are a bit more in-depth.
God's Playground: A History of Poland by Norman Davies. It is one of the greatest book about polish history, definitely worth to pick up. It also gets additional points by being written by a foreigner and less biased in effect.