Although questions asking for book recommendation are promptly closed by the community on Stack Overflow, I am curious if taking it a step further and adding the word "book" to the title filter was ever considered. A quick search revealed that the 20 most relevant questions with the word "book" in them are closed questions; perhaps it makes sense to disallow these questions in the first place, or at least to warn users that their question is about to get closed?
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In this case I'd be against using the title filter. The titles in the book search results are okay. They're not great, but they're descriptive titles. Furthermore, that makes it easy to find questions that are probably subjective and need to be closed.
The title filter is currently being used to weed out a different kind of problem (nearly exactly the opposite). Titles like "regex problem" are almost completely non-descriptive, yet the questions these titles are used on might be perfectly legitimate. The questions themselves are mostly fine and can stay open, but no one will ever find the information that's hiding behind all those crappy titles.
The fact the question is off topic is not related with the title being used; it is related with the topic of the question. You are allowed to use the word book, but you are not allowed to ask for book reccomendations. If the question title would be like the following one, then the title would be allowed, and probably also the question.
The word problem has been banned because they have seen many bad titles containing the word problem. Instead of writing a title that makes clear what the topic is, some users used titles such as "I have a problem," "Problem with my C# code," etc.
You are suggesting something that doesn't even resolve the problem you are described (the questions about the book recommendations), and suggesting to the OP the question could be closed just because the title contains the word book seems a too focused solution. I rather prefer to see a more general solution which alerts the user about the question quality, or the title quality.