Power/runtime weirdness...
I'm certain I turned off the edge before leaving work yesterday. Later that night I took it out of the computer bag and it was warm, but seemingly inactive.
The LCD was black, the track ball light was off, but the eInk screen showed the last PDF document that was opened when it was on, instead of the default entourage splash screen stack of books. This suggests to me the device had started/booted again for some reason.
In this state the power button would turn it "on", at least as much as the trackball light turning on, but the LCD display would never light up, and no button other than Power would cause anything to happen.
Eventually, I got tired of trying to cajole it into good behavior and just popped the battery out then put it back in and the edge started up normally.
When it restarted the system reported 88% battery power.