For all the scholarship on social movements and civic associations, surprisingly little research has focused on the issue of organizational effectiveness. Han's book should go a long way toward filling this gap. Using a mix of comparative case analysis and field experiments, the author offers an empirically rich, analytically compelling account of why some associations succeed in mobilizing effective collective action, while so many others fail- often spectacularly - to do so. This book deserves the widest possible audience in political science, sociology and, most importantly, among those who aspire to successful grass roots activism.