Sklansky, David No Limit Hold 'em: Theory and Practice (188068537X)
The definitive text on this exciting game. Taking a theoretical approach, it covers critical concepts like manipulating the pot size, adjusting correctly to stack sizes, winning the battle of mistakes, reading hands, and manipulating opponents into playing badly. It breaks this complex game down with thorough and easy to follow analyses. It's the ideal read for anyone looking to improve their cash game or tournament play.