The Pandora is super good as ebook reader, you can use it horizontally with one hand (on the left you can scroll with the D-Pad, on the right with Page-UP / DOWN), or vertically also with one hand (scrolling with the touchscreen).
Brightness and font sizes can be changed too, also depending with the program used, many more functionalities can be present.
CoolReader and FBReader are both good... and if you want to take notes and things like that there is Xournal, that with the precision of the stylus is perfect.
Size of your library is no issue with two SD slots and USB ports.
You have hours of battery, and you can also underclock to get even more... you can put it in standby and reopen it as fast as pressing a switch...
Another useful thing is that Calibre is on the repo, and it's a must to manage and convert books from one format to another.
The Pandora it's a completely autonomous device for reading and managing books.
I mean, the only missing thing could be the e-ink display, but it's a pretty specific thing, while all the rest is already happily adapting to the ebooks needs.