Book recommendations are off-topic on EE.SE: Why book recommendations questions are off-topic?, but that is not listed in the not-about items on the What topics can I ask about here? help page.
Other sites, for example Stack Overflow on their on-topic page, do explicitly include that item:
- Questions asking us to recommend or find a book, tool, software library, tutorial or other off-site resource are off-topic for Stack Overflow as they tend to attract opinionated answers and spam. Instead, describe the problem and what has been done so far to solve it.
Please could that be added to EE.SE's on-topic page so that users who diligently read that page don't post a question asking for a book recommendation and then get surprised when it is closed.