I also read the theory, that during the time it was likely written there were a lot of rich merchants and noble men with an interest in the occult, magic etc. So it could be a hoax to sell for a high price as a magic book. After all, there was a flourishing trade in religious relics. Not too far fetched to think that someone who maybe even had the necessary education to make and write books could make up a fake “magic book” and sell it to superstitious duke for a fortune.