Don't use an anonymous email. Just email them from an account you use and see what turns up, if it is such a frequent question the author in this day an age cou

Don't use an anonymous email. Just email them from an account you use and see what turns up, if it is such a frequent question the author in this day an age could post an errata to their website. They might even have a reworked bit of prose for a second edition or some-related-next-project. The only people I wouldn't email are the people that clearly don't want to be found from a simple search. It's just an email, don't overthink it. Don't write a rebuttal essay, just express what you are reading and why it doesn't line up for you and send it along. Maybe there's something you're missing or maybe this is a bit of manuscript that was revised a few times and now doesn't line up perfectly. It's no different than going to a friend and asking if they can make heads or tails from it. They wrote a book to share something they found interesting people asking questions and clarifications is what I would think to be one of the few true rewards.