Be sure to try a Kindle. It sounds like just what you are looking for.
The Kindle's keyboard is a real plus if you are into searching and taking notes on the device. I find it very useful. To find stuff in a book you're reading, you don't even need to type ctrl-f...just start typing.
You mention that light Internet use would be a plus. This is also a very handy bonus on the Kindle, especially if you can swing the extra cost of the 3G versions.
Going out and trying them is a great idea. Any B&N will have nooks to play with and more and more stores have demo Kindles on display.
As for library books, it's announced to be officially coming to the Kindle shortly.
Unofficially, many folks are happily reading library books on Kindles now.
ApK
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