Kei Koga’s book sets an ambitious objective of discovering reasons for changes in the objectives, raison d’être, institutional design, and functions of regional security institutions, studied in a context where superpowers are not the primary actors. Rather, regional institutions are led by ‘ordinary’ states of the region. The empirical focus is on regional security institutions in Africa and Asia: ASEAN, ECOWAS, and the OAU/AU. A theoretical model for institutional change is constructed for the production of new understanding of regional security institutions and their changing roles in regional security. The explanation is based on a rather positivistic logic, and a structural realist ontology. Independent variables for changes are sought from changes in power distribution in the region, and the effect of such changes to institutional change (dependent variable) are filtered through an institutional cost-benefit calculus. The fact that the focus on regionalization that is run by the region, and not by external superpowers, makes it peculiar that the author does not consult the literature of new regionalism, and the theories of Björn Hettne, Fredrik Söderbaum, and Timothy M Shaw. Challenging or complementing this strand of theory of regionalism could have further added to the theoretical value of this interesting book. Overall, this book offers some interesting empirical analysis with some original generic theoretical models that explain changes in regional security institutions specifically in areas where regionalism is led by the region itself. The fact that the book compares two very different regions, and focuses on the inherently regional input in the development of regional institutions makes the book original and innovative. It is essential reading for students of regional security institutions.