The reason I went with the nook is its ability to read different formats.
I bought most of my books from Barnes & Noble anyway.
I had four paperbacks to read before I bought the Nook and I still haven't read them and actually ended up rebuying one of them in Ebook format, It just makes reading to easy.
I have the 3G version so if I am reading a book with a sequel and I finish it and it's a cliff hanger (aren’t they all) I can download the sequel instantly anywhere, and be reading it in moments, which is very nice.
They now offer a less expensive version the uses WIFI only, If available when I got mine, being the cheap bastard that I am I would probably have bought that one.
You can also bring it into any B&N store and read any book free while in the store, they also offer free books for download only in the store, as well as Starbucks Ecoupons for free stuff in the store and special free for Friday books. All B&N stores have free WIFI.
With all that said, they just came out with the new color Nook a couple of days ago. I’m not sure I would have bought that one. It has some cool features but the readability and eye strain of the backlight color LCD screen would not be as good for marathon reading as the eInk screen on my current nook and it uses up the battery quicker. The battery life is awesome I read a lot and only need to charge it once a week.
I don't need all the internet browsing and game features that are included, what I do want and the nook does very well is a device that allows me to read books.
You can also get EPUB books from almost anywhere and there are programs like Calibre that are free that allow you to translate almost anything into a format read by Nook and then you sideload it, by plugging your nook into the USB port on your computer.
http://calibre-ebook.com/Once you have your nook you will have to accessorize it with reading lights and covers (kind of like adding chrome to your bike) I bought my cover from Oberon
http://www.oberondesign.com/nook.php B&N has lots of free books and most new release best seller books cost less than half of the DT (Dead Tree) Version.
http://www.barnesandnoble.com/nook/index.asp?r=1Gutenberg has something like 100,000 free books.
http://www.gutenberg.org/wiki/Main_Page Smashwords has lots of free books and books released by Independent authors, Authors that the publishing houses did not deem worthy of publishing and yet have produced some awesome books. This is where I have been reading most of my books from recently.
http://www.smashwords.com/Hope this helps.
Peter