I will say that in my college classes, the first thing I always do is to download the PDFs of the recommended books to accompany the classes.
Every once in a while one of these books ends up being awesome and truly useful for the class, and then I order it physically because I actually want it in my bookshelf (admittedly I'm not battling poverty).
Such shadow libraries have driven me to buy the books I liked, while rarely opening and reading the ones I didn't need, and also not buying them. It's just like having a "demo" version of a book but without the anxiety of running out of pages.
I think it's already hard enough to engage young people in reading and being into books but without websites like this I think it would be nearly impossible.
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