There *is* a market, but not the one you'd expect
It's for geeks like me. Sorry.
I've got an entire bookshelf of tech books -- the ones that become obsolete in a year or two. All of them are hugely overpriced, not to mention very bulky to lug around. And of course, they're a colossal waste of paper.
Earlier this year, I discovered the joy of ebooks. Instead of having to shell out almost $100 for an obscure COM/.NET Interop book (I did say it was geeky!) and have to wait for as long as two weeks (time that I couldn't afford to lose), I was able to get hold of the ebook for $40 and download it on the spot.
And since those ebooks are Rights-managed, putting one on a reader and then lending the reader to a colleague mimics pretty closely what I'd do with a paper book.
But the best measure of an ebook reader (and so far, I've only held the Sony one in hand) is this one. You can take it with you to the can.