In this book, Brandenburger and Nalebuff use game theory to develop a set of guidelines that will "make it easier to explain the reasoning behind a proposed strategy." The games that they use as analogies do not involve sports with their zero-sum outcomes; instead, they consider a variety of games that allow for mutual benefit, as well as harm, for the players. They use the term co-opetition, which is consistent with their message that cooperation pays off in some situations, competition in others. They encourage readers to think about not only how to play the game, but also how to change the rules. Examination of these games leads them to make recommendations for managers, many of which are relevant to marketing managers. So, to the extent that a game is like a business, this book should be useful. My aims in reviewing the book are to ask: (1) Is it new? (2) Is it useful? and (3) Is it supported? The book has flaws, particularly in the area of supporting evidence, but it is an important book.