How many fake books are sold on Amazon?

A quick search on Amazon for Gerardus Blokdyk will reaveal an amazing author. He managed to publish hundreds of obviously fake books. I purchased one by clicking (mistake) buy on a his book on zero knowledge proof but to my horror I have discovered that he has 400 pages with fake books on many interesting topics. Amazons seems to refund a sucker but this practice could probably hide money loundering or other shady practices...