The gas chambers and crematoria of Auschwitz were the engine of the Holocaust, facilitating the murder and incineration of more than one million people, most of them Jews, in just a few years. Yet such a spectacularly evil feat of engineering was designed not by the Nazi SS, but by a small, respectable firm of German engineers: J.A. Topf and Sons. These were not Nazi sadists, but playboys, and the sons of train drivers. As Karen Bartlett details here, the Topfs were driven not by ideology, but by love affairs, personal ambition, and bitter personal rivalries to create the ultimate human killing and disposal machines—even as their company sheltered Nazi enemies from the death camps by using them as forced labor.