The Jetbook is an excellent ereader that is just an ereader -- no wifi, no browser, no angry birds ... Just download books onto your computer, send them to the Jetbook via a USB connection or copy them to an SD card, and you're set.
The Jetbook will handle just about any ebook format you throw at it, including epub, mobi, prc, etc. DRM does pose a problem, although I believe the Jetbook will handle a couple forms (I'm pretty sure it will handle Barnes and Noble and I think the latest ones will handle Adobe Digital Editions -- double check me on that, since I never use DRMed ebooks). There are plenty of places to buy legal DRM-free ebooks (Fictionwise has a large list of "Multiformat" books that are DRM-free, Baen, if you like SF, many authors' sites, etc.)
I have had a Jetbook Lite for a year and I LOVE it! Biggest difference is that the JBL uses AA batteries (rechargeables work fine) but the JBL was recently discontinued. The Jetbook is the same hardware but uses a Lithium battery that charges via the USB. Still easy to find for about $90.
EDIT: Forgot to mention, the Jetbook will handle Overdrive library books (double check me, since I don't use them). The Jetbook is not eInk, but is very readable (I have family members with eInk readers and I don't like them -- personal taste).
Check out the forums at Mobileread.com for more info on any ereader and for more in-depth discussion.
Edited by Capn Easy, 19 October 2011 - 05:59 PM.