I have an e reader with a back lit screen. You can watch movies and load pictures and music on it as well. I am looking to get a kindle now though as the backlit screen is making my eyes sore. The e reader has over 1000 free books on it that I picked up from various download sites and has the advantage that you can download pretty much any formation book so lower cost and not locked into amazon.
Mines a laser e book. I got a lot of my books off file sharing websites tbh. I am selling the laser to get a kindle now as I am finding reading backlit screen hard on my eyes. though most people just keep telling me to get my eyes tested instead
I have a Kobo Touch. I really like it, use it for purchased books from Kobo, whs and Waterstones plus library books. its easy to use. if you want library books on it (assuming your local library authority does them)you need to use adobe digital editions to get them onto the device. (check out book online on your computer, download file, open in ade , attach ereader to computer and drag book from ade to device).
If you are a big reader, then a nook or a kobo would be best. As mcnorton says then you can download books from you local library aswell as buying them.
Adobe digital editions is a free download and easy enough to install.
I have a very basic kobo and really like after being resistant for ages; it is frustrating when it runs out of power though. I would have got a nook if they were available here when I bought mine not because they sound cute the light is a really good feature.
I have one of the early Kindles with the EInk screen and I think it works well, I find it easy on the eyes. The more recent Kindles and Ebook readers seem to be closer to tablets/iPad type things which is okay if you want to do more than read. I'm not sure what they are like reading Ebooks howerver, because they seem more like a computer screen display.
Our w h smith has now got a kobo section complete with a lovely man to demonstrate the kobos and answer any questions.
I've had a kindle for a couple of years but am seriously considering getting the kobo glo. I like the fact that you can have it backlit or not and its simple to switch, you aren't tied to one company for your books and its easy to borrow books from the library and I wasn't swayed at all by the man in the shop