This article reviews several recent books on the Islamic State in order to understand its goals, motivations, strategy, and vulnerabilities. It argues that the Islamic State's ideology is powerful but also highly instrumental, offering the group legitimacy and recruiting appeal. Raison d'etat often dominates its decisionmaking. The Islamic State's strength is largely a consequence of the policies and weaknesses of its state adversaries. In addition, the group has many weaknesses of its own, notably its brutality, reliance on foreign fighters, and investment in a state as well as its tendency to seek out new enemies. The threat the Islamic State poses is most severe at the local and regional levels. The danger of terrorism to the West is real but mitigated by the Islamic State's continued prioritization of the Muslim world and the heightened focus of Western security forces on the terrorist threat. A high-quality military force could easily defeat Islamic State fighters, but there is no desire to deploy large numbers of Western ground troops, and local forces have repeatedly shown many weaknesses. In the end, containing the Islamic State and making modest rollback efforts may be the best local outcomes.