Controversial means i have to do a lot of research to determine whence the controversy and which side to trust, if any. (Which I don’t have the domain knowledge nor time for.)

Lack thereof, many people agreeing on the contents, is a sign that you can read the book and (sort of) trust it.

Nothing guarantees nothing, cogito ergo sum and all that, but it’s a good heuristic.

“In my mind,” of course ;)