Exactly what the subject says. I'm suggesting that things be coded such that listings for books will automatically have all of the tags present in their chapters added to their tag list, preferably with no human involvement required. And yes, this would include controversial tags, because if 3/4 of the chapters in a book have the loli tag, the book itself probably should too.
It might be a good idea to indicate how many chapters each tag appears in, so folks won't buy something only to find that their favorite kink only shows up in one chapter at the end or something.