I totally disagree with the other reviewers who say this book is "no longer relevant". It is the definitive guide to Blackjack's "Basic Strategy" plus provides a fascinating historical perspective on how Thorp ran the computer simulations to develop the Basic Strategy and test it in Nevada casinos back in the early '60's. What the other reviewers say is true, that the methods Thorp used (card counting) to make a lot of money back in the '60's no longer work today, but that doesn't diminish the value of the book. The casinos were changing the rules and "shutting down" the big opportunities before Thorp even finished the book. But that isn't the measure of the value of the book (although it is testimony to how powerful Thorps's insights were when first developed).
Everyone playing Blackjack (one deck or out of a shoe) should be playing "Basic Strategy" at a minimum. If you want to implement some other strategy on top of that (changing bet size, card counting, etc. etc.) have at it. But the starting point should be Basic Strategy.
Furthermore, the average recreational Blackjack player should be playing Basic Strategy, but many (most? -- at the cheaper tables anyway) don't as you can observe by sitting down at any Blackjack table.
This book should be read by anyone who wants to play Blackjack.