The 15 books are: The Castle in the Forest tells the story of the young life of Adolf Hitler, his origins and his immediate family tree, through the eyes of what at first is portrayed as a young SS officer researching Hitler's genealogy at the behest of Heinrich Himmler, who opens the novel speaking to SS officers about the importance of strong traits that result through incest.

Following two marriages and a number of affairs, Alois marries a relative, either his niece or his daughter, Klara, and the couple have three children who survive past childhood, the third of these being Hitler, who is referred to by Mailer as Adi.

At this point, Dieter reveals himself to be an employee of Satan, instructed by his superiors to oversee the development of Hitler for possible use by the devil in the future.

The New York Observer called it a "blackly hilarious, beautifully written book" while Entertainment Weekly wrote that it was "terrifically creepy... an icy and convincing portrait of the dictator as a young sociopath".

The Boston Globe wrote that the novel was "saturated with a very material sense of evil: The moods, textures, auras and above all the smells that announce the entrance of the Devil into earthly affairs."