This is definitely a rare case of a book more famous for the person who read it than for anything in the book itself. The book itself consists of discussions on magical powers, their origin and their supposed 'history'. It does not take a scientific approach to this endeavour. The bulk of this book is a sequence of opinions with little to no supporting evidence.
But what actually is Schertel's theory? Well, it's remarkably Hegelian. Certain symbols, objects and practices are given meaning by a collective understanding of their nature as 'demonic' things. These meanings are effectively constructed culturally through mutual understanding. Thereafter, those with the 'demonic seed' within them, are able to channel the energy of ecstasy through these objects and rituals and realise creative energy in the world. However, only a very small number of very rare people are able to become true creative 'magicians'.
So yeah, so it's pretty wild stuff. The introduction is quite fun, particularly the part that makes the book sound as though it has Necronomicon-esque powers:
After several years various translators have come and gone, some holding the book for months and accomplishing nothing, while others translated just enough to figure out they found the subject matter too disturbing to continue.
There's a ton of other stuff about the demonic giving way to the angelic, and the path from being a demon to a seraph. It's all pretty esoteric. Although, I do sense that if Hitler hadn't have kept an annotated copy in his library, nobody in the twenty first century would be paying this book any attention at all.