Based on their review of the various research methods, the authors recommend a collaborative, mutli-method research approach that exploits the advantages of the various specific methods. And they outline a revised theory of collective action focused on individual decision making affected by micro-situational conditions and broader social-ecological contexts.
In addition, the authors provide a very useful discussion of an important practical issue for social scientists, who might incline to the kind of collaborative, multi-method approach the authors recommend. As the authors explain in the Prologue:
It is often difficult to acquire data relevant for the study of collective action, and the costs of field research are significant. Scholars are also constrained by the costs of mastering multiple methods. Collaboration facilitates both comparative research and the incorporation of multiple methods, but presents its own challenges. We are particularly troubled by professional norms and career incentives that discourage collaboration and multimethod research and fail to acknowledge the practical challenges that affect methodological practices.Simply put, academic collaboration itself is a collective-action problem, which is exacerbated by the "fragmentation" of academic disciplines, distrust between academic departments, and tenure and promotion processes that struggle to evaluate and reward collaborative, inter-disciplinary work.
Bottom line: This is quite probably the most important and useful book about social-science methodologies to be published in several decades.