You seldom get a book which is so admirably clear in its thesis, explains why competing explanations are lacking (in a more conventionally academic book we would have had to dredge through chapters of the author engaging with nonsense in detail, in this book this is dispensed with in a few paragraphs pointing out how deficient these theories are) and then goes on to show systematically how his explanation is much more convincing and action guiding. Because of the visceral subject matter and stories the author can rely on this never ceases to be anything but a fascinating read, even though he (commendably) makes his basic points up front and then the rest of the book is mostly repeatedly showing how these points relate to different aspects of prison life and culture. The author never glamorises the subject but never demonises it either. Thus he can credit prison gangs for dramatically reducing the level of violence in American prisons, while also highlighting the misery and evil they fuel inside and outside of prisons. I would have liked the last chapter to be even more ambitious and have explicitly suggested lessons from the study not only for prisons but for other areas of informal governance.