Theory of Poker is far and away the best book on poker ever written. Well, I haven't read them all, but enough other people have also said so that I feel comfortable agreeing. If you could only read or own one book on how to think about poker, this should be it. Sklansky doesn't just tell you what to do to maximize your expectation, he explains why what he says is correct, where appropriate using simple mathematics explained clearly enough for anyone to understand. There is an enormous amount of absolutely essential material in this book, enough that the book stands up extremely well to many repeated readings. It is only a mild exaggeration to say that everything you believe about how to play optimal poker should follow in some way from what Sklansky writes in this book. And in a market glutted with poorly written poker books, Sklansky's writing in Theory of Poker is relatively clear and concise.