First of all, those who are not into technical reading will find this book slow going. Browning documents Police Battalion 101 with a high degree of detail. Throughout the book there are pages listing the number of Jews forced into ghettos and eventually camps and the kill tallies for particular days.
Browning wants to know how middle-aged German men could have become mass-killers on multiple occasions. The majority of the book is devoted to the battalion's activities during the Nazi era. The details are given in a semi-detached manner but it does nothing to take away from the horror of the events. The final chapter explores the theories of mass violence and what Browning believes happened with Battalion 101.
Browning does an admirable job of presenting an extremely difficult subject. There are a lot of books on the Holocaust (many more than I could ever care to read) but this is definitely one worth reading. Even for those not particularly interested in Holocaust history might be interested - or horrified - by how easily kill squads can be created under the right circumstances.