Today I received a book I ordered from Amazon. Principles of neural science is a 1,400+ pages book.

The book is heavy, so heavy that it is almost impossible to carry it in my backpack; I have no idea how many trees have been cut to print it, and how much energy has been used to ship it, but the point is: if a device based on e-ink technology allowed me to read decently on A4 format, I would be more than willing to download a PDF and store many of these "books" in the device.

The closest to a device like that is the Iliad, which is not available yet.