Whats the best book on poker between Hansen and Al Harrington?

Dan Harrington is the man if you are learning the game. Gus's book is a great read but it won't teach you how to play good poker. You won't get very good at poker if you only buy one book though, there is always something new to learn. I'd also recommend Sklansky's "The theory of Poker" when you've got the basics down and played a few thousand hands.