A simple sanity check would be to run the exact same analysis on different books, and compare the book to the population. It would of course not be definitive,

A simple sanity check would be to run the exact same analysis on different books, and compare the book to the population. It would of course not be definitive, but, for example, if I had seen that only 1% of the books on amazon have this many people mentioning professions on reviews, I'd get suspicious.