For the last twenty years, Rees has interviewed dozens of former members and supporters of the Nazi party, in an effort to understand the causes of the spread of Nazism in pre-war Germany.

These personal testimonies form the basis of this book, as through the narratives of people who experienced Nazism and Adolf Hitler firsthand, an interpretation of the phenomenon that led to the barbarity of the extermination of the Jews and the deadliest battles in human history during the conflict between Nazi Germany and the Soviet Union is attempted.

The book has been particularly praised for the way it approaches and sheds new light on thorny and difficult questions regarding the politics and ideology of the Nazis before and during World War II.