This was my first Mailer novel, and from what I've read - both between the covers of the book as well as the reviews here on Amazon - I chose poorly.
We're led to believe this is a story of Hitler's formative years. When you look at the bibliography, it seems Mailer intended (and produced) something of a historical fiction. However, while we see much of Hitler's ancestors (particularly his father and his difficulties with the zipper), and a little of the young "Adi", it almost seems to me this is more of an musing on the workings of good and evil - God and the Devil, from the Devil's perspective - with an infamous product of this struggle as context.
If I were to Twitter a riddle regarding Castle in the Forest, I might write, "What do you get when you cross The Rolling Stones (Sympathy for the Devil), Freud and Oedipus Rex?"...Continua