This question crops up again and again in some guise or other. Probably impossible to answer in the context of this forum with any level of objectivity, so I wonder whether it's worth putting a subforum together on this subject with a sticky thread with some standard recommendations?
(As for me, I haven't got a clue about books at a basic level, so someone else may be able to help out here.)
Also, what might be useful would be a sort of "aptitude test" that would-be questioners could give themselves, e.g. "Was this question easy? Then such-and-such a book would be beneath you." Or: "Was this question incomprehensible? Then leave so-and-so book alone, it will be way over your head."
Yes I know, this is likely to be a tall order and a large project. Does anyone know of such a project? Is anyone interested in collaborating on one to set such a resource up?