He is assuming that the flash memory in the e-reader is in a chaotic state and is only ordered when an e-book is written to it. This is not true. By the time you get the e-reader, every cell in the flash memory has probably already been written to at least once (either when the flash memory chip itself was tested post-manufacturing, or when the e-reader software was imaged onto the device). Because it must deterministically return the value written to it, even if the new owner doesn't know what that value was, the e-reader is already "holding stationary" all the electrons in its flash memory gates.
Also, while operating, there is a constant flow of electrons in and out of the device, with energy removed from the electrons and converted to heat (with useful functions a byproduct of this conversion). Since the flow of electrons is not perfectly constant, the mass of the device is constantly changing due to how many electrons are within it at any given moment. This fluctuation is of much greater magnitude than the alleged effect.
5.