Ask HN: How to judge a (nonfiction) book before buying it?

I come across books that sound interesting, but always want to check out reviews from people who have read it before me before making the decision to buy it.

What is your process to evaluate if a nonfiction book is worth buying or not?

Do you have a process to evaluate this? Do you have a sequence of things you check, for example, the table of contents, the author's history, etc?

Is there something specific you look for when you buy an e-book?