Would you think a book recommendation would be a great idea, or not?
Book recommendation questions have a tendency to invite multiple subjective answers and fall under the "primarily opinion-based" close reason which applies on all sites:
Furthermore, we can learn from the experience of previous incarnations of the Literature proposal. Quoting from this answer from 2011, relating to an older proposal then named Books and later renamed to Literature:
And a comment on that same answer from a member of that failed incarnation of Literature:
This is almost exactly the point of the example questions: testing the scope of the proposal and demonstrating what the proposal is about and not about. If you want to know whether something would be considered on-topic or off-topic, propose it as an example question.