In the three decades since the appearance of Kenneth Waltz’s seminal Theory of International Politics, scholars have been grappling with his sweeping thesis that international anarchy creates a general tendency for states to compete, balance, and forsake cooperation. Various schools of realist theory have emerged -- offensive, defensive, classical -- to explain complexities that Waltz’s general theory misses, such as the failure of states to balance, the absence of great-power war, the peaceful end of the Cold War, and the extraordinary postwar upsurge in institutionalized cooperation among the advanced industrial states. In this important study, Glaser attempts to reassemble the various realist pieces into a new comprehensive theory of conflict and cooperation. He focuses on three sorts of factors shaping security strategies: the motives of a state, its material capabilities, and the information it has about the capacities and intentions of others. Out of these variables, he fashions a rationalist theory that deduces the circumstances under which states will seek to cooperate or compete. The result is a novel synthesis of realist theory that will provide a useful baseline for future research and debates. The critical move Glaser makes is to distinguish between “security-seeking” and “greedy” states. The first type is motivated to overcome suspicions and cooperate, whereas the second is aggressive and willing to risk war. The problem is that this argument begs the question of why a state is one way or the other, the answers to which lie outside of Glaser’s theory. For readers less interested in academic debates, the book will nonetheless be interesting for its clear-eyed portraits of great-power politics, including the shifting power relations between China and the United States.