It isn't an obvious response, but I would suggest replacing the internal SD card. From my experience, plus a lot of reports here, the cards in the Glo are getting old, failing and causing all sorts of weird issues. When it started for mine, the device would hang and restart randomly. You can create an image from the current card and try that, or I can supply an image to use. Other problems such such as the database on the device getting corrupted frequently are also a strong indicator of a failing SD card.
Other than that, random seeming sleeps can be because there is a magnet of some sort near enough to trigger the cover. That usually happens when putting the device down somewhere rather than while reading. Some of the newer devices have had issues when the cover is completely open. That seems to be related to the strength and position of the magnets in the cover. I don't think I have seen it reported with the Glo. But, turning the sleep cover option off would let you test if this is happening.
Holding the power switch in the off position for 20 seconds should force the device to turn off without updating the screen. After that, you need to turn it on. I haven't seen this not work unless something really bad is going on. Though, the switch on my Glo has worn down enough that it can be slippery.
The pinhole reset button only has an effect if the device is on. If the device has been powered off, it won't do anything.
And you probably should stop reading here...
My first thought when I saw the thread was, "Then stop reading boring books".
