You've already discovered the remarkable tablet so I'm just going to say that I'm a huge fan. I use it quite heavily for note taking. I can't recommend it enough. You may find second hand units for cheaper, since they've been around for a couple of years now and there exists a large majority of people who weren't really heavy paper users but bought it for the sake of novelty.
That said, if your primary problem is going through a lot of books quickly and you cannot afford the remarkable, even a used one, you may want to consider something like:
One of my colleagues uses it and seems to be pretty happy with it.