Just found a book that you might want to read but you aren't sure if there's questionable material? Here's what you do...just quickly flip through the book, scanning a page here and there, looking for objectionable words and descriptions. It's not fun to come across these, but it's better to come across it quickly in the act of skimming instead of intently reading the book.
If a book doesn't pass the flip through test, don't read it!
If it does pass the flip through test, it's not a guarantee that it's safe, but it's better than nothing!