I have a Sony PRS-505 and I doubt I'll but a paper book for a long time.
I've read four and a bit books on it so far and I find it so much more comfortable to hold than a paper book. I find I get less hand cramping when reading for a long time.
I downloaded a program called calibre to sort the booke out and arrange my library since the software that came with it does not work with macs. Or maybe it does, in any case I didn't even look at the CD since I read that calibre was better.
Once I get a waterproof cover for reading books in the bath it will be perfect. Paper books don't work well in the bath. I know from experience and ruined paperbacks.
One thing. I wouldn't prefer it to a textbook at all. To study, I'd stick with paper.