E-book readers like the Kindle may be getting better, but still fall short of the usability of paper books. You can't turn or flip through pages, or compare different documents as you would with paper. A new prototype with two displays can do all that - as the video here shows.
The two leaves can be opened and closed to simulate turning pages, or even separated to pass round or compare documents. When the two leaves are folded back, the device shows one display on each side. Simply turning it over reveals a new page.