johndoe said:
Look, whether there is a legal barrier to posting indicies is very different than whether it's polite to do so or not. Legally, sure, it's probably not copyrightable. But really, just go and buy the book already. It's worth it.
A book about avoiding detection would be worth more than any other blackjack book if full indices were posted online. Even tips about avoiding detection are not copyrightable.
It looks like the only thing that is copyrighted about non-fiction is the way that facts are expressed by the author: https://www.artslaw.com.au/article/a-matter-of-fact-non-fiction-and-copyright/
If you want to give advice that comes from a book, all you have to do is reword the advice to avoid copyright infringement. You could read a book about avoiding detection as an advantage player in a casino, and repeat the advice using your own words to others. Facts are not copyrighted. Only the way a fact is expressed by an author is copyrighted.