(Rather than revive several old threads, where people were asking, in here,
if this was possible...)
I'm just making this post to warn everyone that, as far as I can understand,
it's now already possible to have an e-book reader running only Free
Software.
There was a Polish hacker who managed to make the Kobo readers - that are
sold in Europe and North America, at least - run a modified version of Debian
that, from what I understand, doesn't include any proprietary blobs.
http://www.mobileread.com/forums/showthread.php?t=222123
(It's an already 2-month-old piece of news, and, I'm sorry for only posting
this now - since, I've known about this since a few days after it was
announced - but, I've had a lot of other things in my mind, lately...)
The mini version of Kobo is sold (in my country, at least) for as low as 40
euros.
Happy hacking. :)