Haven't been playing any serious poker for a while, but I'll tell you my favorites.
First, I'd recommend David Sklansky's Theory of Poker for a good overview of the terminology and math that relates to the various poker games. It's definitely more technical in nature than some poker books, which is a problem for some, but anyone who understand BJ math shouldn't have any trouble following it.
Second, if you are playing limit holdem, get Small Stakes Holdem by Ed Miller, David Sklansky, and Mason Malmuth. That book made helped get me up to a respectable LHE winrate back in the heyday of online poker, although I never played anything but small stakes. Don't let the "small stakes" in the title fool you though. It has great strategy info, and obviously the level of your competition matters much more than the actual dollar amounts.
Finally, NLHE. This was not my best game, but it's what I've been playing lately. I haven't really dedicated enough time to learning this game because I haven't been spending much time playing it. I have however read Professional No Limit Holdem, Vol. 1 by Matt Flynn, Sunny Mehta, and Ed Miller and can definitely recommend it.
With TOP and one of the others depending on your game, you'll be well on your way to earning money at holdem. Also, I used to post quite some time ago on twoplustwo.com. I haven't been on there lately, but it was a great resource as long as you can sort through the advice and figure out the reliable posters (just like any web forum). My experience (and that of my poker playing friends) has been that any book from Two Plus Two is generally worthwhile.
What game do you expect to play? Roughly what stakes and player skill level? With that info, some people might be able to give more specific recommendations.