If this error message appears on a Kindle, the remedy suggested by Amazon is to 1) unplug the Kindle if it is charging, and 2) then perform a hard reboot by pressing and holding the power button at the bottom edge of the device for 30 seconds (counting slowly) and then releasing it.
Do not press any other buttons or interact with the touch screen while the device reboots. It may take a few minutes for the books to reappear.
If the Kindle is still unresponsive, please return it to the Ford Library circulation desk during the business day (M-F, 8am - 6pm).