I closed that question. Why? A few things:
- The title is asking for the best book, which is very much based on opinion
- Even if we did allow book recommendations, they should be more specific. This question, as it is, is quite subjective.
I do agree that we need to better define what recommendations we allow. However, this question could, and should be closed as either primarily opinion based or too broad. Both would fit.
As far as a recommendation that's clear and specific, I'd say it should be allowed. A lot of questions currently are "recommendations" because they ask for libraries/parts/software. This is a list here (adding to another post for CW).
I don't think it should be upvoted, deletion isn't used in this case (and is automatically done by the Community ♦ user after a while), but you can downvote if you want to. I'm not going to advise you on how to vote. :)