It's been (slightly) bugging me for a while that we have two tags for questions about reading material, books and reference-request. I've never been quite clear about what the difference is, or should be. Do we even need both these tags? If so, what exactly would each of them be for, and how do we distinguish between them?
For reference, the meanings I've been using so far are as follows:
- books is for questions asking "What is a good book about X?" or more generally, "What should I read to learn about X?", typically where there is not a single authoritative reference. These sorts of questions have multiple answers and will acquire new answers as more books/papers are written on the subject, so they are almost universally community wiki material. Examples include anything listed at Book recommendations.
- reference-request is basically for questions of the form "What paper explains effect X?" (example) or "Where can I find the derivation of X?" (example) or "What is the original source for X?" (example), etc... basically any question which is looking for one particular paper, or a short list of papers (or books). A decent but imperfect guideline seems to be that for these questions, all or nearly all of the references that could be posted as possible answers already exist at the time of the question being asked; we don't expect a steady increase in the number of valid answers as time goes on.
I'm not saying that this should be the distinction between the two tags, but it is one possibility. I'm aware that these rules are not always completely clear, which might be a reason to reevaluate the meanings of these tags.
If we go with this, an interesting borderline example would be 1-form formulation of quantized electromagnetism; I'd be curious to know which of the two tags concerned people would apply to that.