The "so what" is that I don't expect incoherent gibberish to have similar statistical properties to actual language. If the book is written in a language (or c

The "so what" is that I don't expect incoherent gibberish to have similar statistical properties to actual language. If the book is written in a language (or constructed language or cipher) then we have no more reason to expect its author was mad than we have to suspect any random author of any text we can't read is mad. And maybe coherence isn't binary (not that I ever wrote it was) but TempleOS is clearly an example of something that is coherent though done by mentally ill person for an irrational purpose.