For me, it's the portability. I travel a lot for work and am an avid reader. The ability to carry hundreds of books with me is the selling point for me - paper books are never going to be able to offer that.
As an example, I was stuck in Germany when the ash cloud descended. If I hadn't had my e-reader with me, I would have run out of things to read. For me, that's not far away from running out of air to breathe
