I had to study entire books just for a single exam.
So what I used to do, was that I just forget it was for an exam, I just thought it was going to be a simple read at all. Said that, the perception of stress vanished. Next what's to recognize the important info during the read. In case I need to remember it quickly, I just wrote notes about them. But after finishing the book, restudying was very easy.
And like Ashley said, breaks are necessary. I used to take them after 45 minutes of studying, because you know, in case you're reading and you feel like you don't pass over that segement, it's better to do something else, and after 15 minutes, return back to the material. It's worse to be studying and don't remember anything of the material, than relaxing and then remember a lot of it.
Making AMVs by day, Going to Gym by Night