I'm a convert to the selective approach. I started out by downloading everything (I'm sort of a hoarder by nature).
But then I realized that it was just obscuring the ones I really wanted to read most. I figure I can always come back and look for more, and what made the books most interesting to me was the book blurbs on the post, so I'd come back to the original post anyway.
If it was worth the effort, probably the smart thing to do would be to add metadata to the file for my rating of how much I want to read it, and a description of why it was interesting to me. But that's overkill, so I stick to just downloading the ones that I am tempted to read next. (Even so, that is a lot of books, of which only a few will become the "real" next books I read!)