From [Bookeen] Official answer for battery and some general information
When connected to a host machine through a standard mini-USB cable, the Cybook is seen as an external mass storage device. You just need to drag and drop your files in the device memory and you can start reading.
Note that the base system might require USB connection to recharge (once a month or so), since a stand alone charger is only provided with the "Deluxe" version. So a computer of some kind is needed to charge and to download e-books - not a major issue these days.