There are so many books to read... I would like to hear whether you think it is more beneficial to read widely (i.e. many books) or deeply (study intently very few books). It is perhaps an impossible question, but I would appreciate some food for thought...
I think it's a bit like how Madeliaette said above. There are books that you can read without studying and there are those you can study. If you have a more general book, directed to a wider audience, then probably you can read it once and it suffices. This sort of books helps you getting an overall picture about Buddhism and its community. You get a sense of where you are, where you're headed, what others do and that sort of stuff. They help discovering the overall "environment".
Then you have literature about the teachings. Here deepness is the most important factor. Read and contemplate, clarify your doubts and reread doing the whole process again until you feel you are completely at ease with that particular teaching. Put it in practice if that's the case.
It's good to be following a certain direction when choosing these books. Generally it's wise to ask advice to one's teacher about what would be more beneficial to study.