Researchers from Berkeley and the University of Maryland have built a dual-display e-reader prototype that uses traditional book-reading navigation (i.e. page turns, flipping the cover under, etc.). From the New Scientist:
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.
The following video shows the e-reader in action: