Book excerpt: This investigation into the Nazi leader’s mindset is “an inherently fascinating study . . . a work of meticulously presented and seminal scholarship”(Midwest Book Review). Adolf Hitler’s virulent anti-Semitism is often attributed to external cultural and environmental factors. But as historian Peter den Hertog notes in this book, most of Hitler’s contemporaries experienced the same culture and environment and didn’t turn into rabid Jew-haters, let alone perpetrators of genocide. In this study, the author investigates what we do know about the roots of the German leader’s anti-Semitism. He also takes the significant step of mapping out what we do not know in detail, opening pathways to further research. Focusing not only on history but on psychology, forensic psychiatry, and related fields, he reveals how Hitler was a man with highly paranoid traits, and clarifies the causes behind this paranoia while explaining its connection to his anti-Semitism. The author also explores, and answers, whether the Führer gave one specific instruction ordering the elimination of Europe’s Jews, and, if so, when this took place. Peter den Hertog is able to provide an all-encompassing explanation for Hitler’s anti-Semitism by combining insights from many different disciplines—and makes clearer how Hitler’s own particular brand of anti-Semitism could lead the way to the Holocaust.