I just got 3 books (some were short so~700 pages total) out of a charge, 5 days. I downloaded 14 books using wifi during that time frame. Not stellar but I'm content.
One thing to note. I don't charge unless the device tells me to. I get at least 150 pages after all the battery bars are gone. Also, make you charge until battery display is solid black. It will revert to bars when you unplug it.