I have one of the Sony Readers. I’ve spent the last 4 years with no fixed address, and wherever I went I accumulated books (boxes and boxes of them…). After being forced to leave £150 worth of hardcovers in America, I stumped up for the Reader.
One of the best things I’ve ever bought. Millions of books on Sony’s US site, countless more available online, and even more available for free (Heart of Darkness, etc). Even better, many of the books I already own are up for grabs on more dubious websites, and I have those with me now too.
My Reader has over 80 books on it, along with a daily digest of all the Guardian web articles, and a couple of gigabytes of music. Cannot recommend it highly enough, although if you have somewhere to keep your books I can’t really see the point of buying one.