Take your time as you look into the EBR world. If you're like I was a few months ago, you have no idea that Kindle=Amazon and Nook=B&N. I was that clueless. So you can imagine the confusion that DRM tossed into the equation.
As a frequent library user, I anticipated using an ereader (EBR) and the library extensively. As it turns out, my EBR and library usage have had very little interaction due to:
1) lack of ebooks available that I have an interest in
2) lengthy waits to get what few books I would like to read
3) the *HUGE* amount of books I've been able to get for free and/or very low cost has built a backlog of reading that will probably last me several years.
(and I keep adding to it)
I found that I developed distinct preferences as I looked at the various EBRs available, most notably, the Kindle3 and the Nook. I have come to develop an appreciation for the Sony EBRs, but their current lineup tends to be pretty pricey and only the top dog has wifi, which I wanted to have.
I don't know that I'll use some of the features that distinguish the Kindle from the Nook (such as highlighting across multiple pages, text-to-speech, ease of getting to searched items, etc.), but I like how the K3 works and I especially prefer a physical keyboard over a virtual keyboard as implemented on the Nook. Sony allegedly has a nice touchscreen, but other than the iPad, my TS experiences have generally left me frustrated.
Get to a BestBuy or similar where you can find the Kindle, Nook, and Sony EBRS side-by-side and spend some time working with each. You may well prefer a TS to a KB. Wifi may not be important to you.
Another good option is to search YouTube for videos of various EBRs. The virtual experience was very valuable to me as I could see how the various EBRs worked in daily use.
Here's a sample video comparison:
http://www.youtube.com/watch?v=jgr_dGNW1sA
Because I found that I developed a specific preference for the Kindle (although I started out to get the Nook)... and in anticipation of wanting to borrow library books and read them on the Kindle (before I discovered the limitations of doing so), I researched and learned that with some software and my PC, I could read the books of my choice on the device of my choice. Now I can buy ebooks from Borders, B&N, Amazon, etc., borrow books from the library and read them on my K3 without issue... which, imo, is the way it should be.
Regarding readability of the various devices, I find that it's easier to add light (as in nighttime reading) than to take away light (reading in bright sunlight). I tried a Nook Color outside on a bright sunny day and could not read the screen. If you can, take the EBRs you like to a very bright setting and see which you prefer.
Good luck.