Unusual genres and subgenres of books

[Harpo]

I’m hoping to find an as-yet-unobserved world of bizarre hybrid subgenres of books, which collectively might point ways towards some unknown far horizons of knowledge.

Here’s an example - I have a book called Exploring The Edge Realms Of Consciousness which lists on the back the genres “Metaphysics” and “Parapsychology”.
Never mind the book itself, I am interested in the genres being listed. Like anyone browsing in a bookshop seeing such a book is going to be persuaded or dissuaded because of “metaphysics and parapsychology” being indicated.

So, given such an example, what others do you know about?

 

[hitmouse]

The Expert at the Card Table by SW Erdnase.

There is about 120 years worth of cultish obsession, and hundreds of books plus a few films, directly and indirectly stemming from this single slim volume on how to cheat at cards.