Peter Levenda is an American author who focuses primarily on occult history. He is best known for his book Unholy Alliance, which is about Esoteric Hitlerism and Nazi occultism. Occultist Alan Cabal wrote in 2003 that Levenda was the writer with the pseudonym of "Simon", the author of the Simon Necronomicon, a grimoire that derives its title from H. P. Lovecraft's fictional Necronomicon, featured in Lovecraft's Cthulhu Mythos stories. The United States Copyright Office registration for Simon's Gates of the Necronomicon lists the author as Peter Levenda, whose pseudonym is Simon.
https://en.wikipedia.org/wiki/Peter_Levenda