"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."
Read their paper on it or just go look at the video.
I suspect that when you're done with the book and want to close it you turn the device upside down and shake. :~)
I'm still waiting for the e-paper version.