Ensuring quality when you randomly generate things is hard.

I made a word generator tool. In doing so, for just 6-14 letter words, I had to develop a large amount of quality regulation formulas that would detect unnatural patterns ("xamxo" for instance might be a questionable pattern to have in a word).

Anyway, the thought of coming up with a generator to make a whole book (at least one that is coherent) is an interesting one - and much, much more challenging.