Every once in a long while a major puzzle in the study of politics and economics is solved. Baccini and Urpelainen have done just that in this important book. Through careful political-economy theorizing, clear quantitative analysis and penetrating, theoretically-sophisticated case analysis, they explain when international institutions effectively combine with domestic political conditions to promote economic reform and when they do not. They make a powerful and thoroughly convincing case for the advantages that preferential trade agreements with the United States or the European Union can have over multilateral arrangements or bilateral agreements with states such as China. They show clearly how international institutions can serve as credible commitment devices for leaders facing stiff domestic opposition to reform. Anyone interested in development must read this wonderful book.