The author treats both concisely and profoundly the complex phenomenon of political extremism. This is certainly one of the best summaries of the subject.

Short book attempting to define extremism, give a bit of history, and explain what extremists do. Extremism in this book is defined as the belief that an in-group’s success or survival can never be separated from the need for hostile action against an out-group. Of course, the concepts of in-groups and out-groups are gone into a lot. A little attention was given to the psychology of it all, but not nearly enough. Even though huge masses of people suffer in all sorts of ways only a few become extremists. Why? That’s what I’d like to know more about. ( )

This short book is exactly what I hoped it would be: a brief overview, some theory to move understanding beyond definition by example, some discussion of current thinking and issues, and a curated list of sources for further reading. I particularly appreciate the effort put into definitions and theoretical framing, which propose a path for moving beyond reflexive thinking about current threats.

Of course a book this small isn't comprehensive or the last word on anything. That's not its purpose. It is, however, an excellent starting point and shortcut to understanding a few key issues whose misunderstanding is at the root of many failed initiatives. ( )