aka Kindle. From Amazon.
Jeff Bezos was talking to Charlie Rose about it last night. It uses real ink, not a computer display:
Utilizing a new high-resolution display technology called electronic paper, Kindle provides a crisp black-and-white screen that resembles the appearance and readability of printed paper. The screen works using ink, just like books and newspapers, but displays the ink particles electronically. It reflects light like ordinary paper and uses no backlighting, eliminating the glare associated with other electronic displays. As a result, Kindle can be read as easily in bright sunlight as in your living room.The screen never gets hot so you can comfortably read as long as you like.
Neil Gaiman, author of Stardust, "It's like paper and it’s very interesting. It’s very, very crisp. Very functional. Very readable."
But how do you buy used e-books? I doubt people can resell their copies due to piracy concerns. Of course there are ways to do it, but Amazon probably doesn't feel like cutting into e-book sales, at least not yet.