The "Nook" is Barnes & Noble's e-reader. The Nook runs on Google's Android platform, has 2GB of memory built in and a microSD card slot, and can play MP3 files, photos and more. It supports ePub, PDFs and more formats. There's free wireless in the US (via AT&T) and Wi-Fi, too.
E Ink display info:
6" E Ink, 16-gray levels (there's also a 3.5" touch LCD)