Collective action problems are ubiquitous in situations involving human interactions and therefore lie at the heart of economy and political science. In one of the most salient statements on this topic, Elinor Ostrom (co-recipient of the 2009 Nobel Memorial Prize in Economic Sciences) even claims that “the theory of collective action is the central subject of political science”. The current volume, Modern Dilemmas: Understanding Collective Action in the 21st Century, is a collection of essays which target the problem of collective action from both a theoretical and applied perspective. The volume consists of four parts, each of these providing insights into different research fields. Thus, the first part, Theoretical Approaches, offers a guideline to the study of collective action in public choice theory and rational choice institutionalism and shows how it can be connected to other research programs such as constructivism, social network analysis and contractualism. The second part, Collective Action and Responsibility, tackles issues specific to political philosophy such as collective and individual responsibility and the morality of free-riding behavior. The third part, Collective Action and Public Policies, presents empirical studies on collective action in relation to educational policies, health policies and policies which target food security. Finally, the fourth part, Collective Action, Political Institutions and Social Movements, consists of various studies on classical problems of collective action such as political protests and revolutions, but also problems which are not traditionally associated with collective action such as party funding and the role of international organizations in economic recessions. The multidisciplinary character of the volume therefore makes it an interesting reading for students and scholars working in a number of different areas of study, such as political science, economy, political philosophy, public policies, comparative politics and international relations.