Full books and for me the ability to have any size font is wonderful.
I also have a folder with a built-in light which means I can read it in any light conditions. I have the 3g version which gives me internet access on the move. I also have the PC version as well, which gives me colour if needed .
I recently got one and I have to say it is brilliant. I got it from Amazon as a refurbished one (see link below)
http://www.amazon.co....&tag=theans-21
You don't need colour to read books and the battery life is fantastic. Two weeks and still no need to re-charge it.