If you are fairly new to the game I would suggest picking up Theory of Poker by David Sklansky or Phil Gordons little green book to get a basic foundation.
For limit I would recommend Small stakes Holdem, by Sklansky and Ed miller. This is the first book I ever read, since I was once a limit player. It was very good and explains a lot of poker concepts in detail.
For no limit cash my favorite books were Professional No Limit Holdem, No Limit Theory and Practice, and Harrington on cash games. There is also a free 6max NL strategy guide online at Free 6 Max NL Strategy Guide
that is pretty good.
If tourneys is your thing, Harrington on Holdem volume 1 and 2 is the holy grail of tournament books. There is a few others that I would also recommend, such as Kill Phil, Kill everyone, The tournament poker formula, and Sitngo Stratego by Colin Moshman is a great book for single table sngs.
edit: I don't recommend super system for someone just starting out. It was one of the first books I read and I lost quite a bit of money using his fear equity strategy. It doesn't work very well at microstakes