Hmmm, OK, thanks. It IS pretty annoying, seeing as how that's kind of counter-intuitive. It's exactly when I AM reading that I'm most likely to rely on the auto-sleep feature.
Think about it: If I'm reading and I get interrupted for what I think will be just a moment, I'm not going to exit the book. If the interruption turns out to be longer than expected, that is exactly when I would count on the auto-sleep feature to activate itself.
On the other hand, if I KNOW the interruption will be longer and I therefore take the time to purposely exit the book, then I am obviously more likely to also immediately turn the vox off or put it into sleep mode myself, right then and there, rather than waste another few precious minutes of battery life waiting for the auto-sleep feature to activate itself.
As for not wanting it to turn itself off while I am reading, I (and most users, I'm sure) already took that into consideration when I set my auto-sleep period. I chose 5 minutes, but if I needed longer I would just select a longer period. I thought that was why they gave us that option.
But it is good to know this is an intended "feature" and not technically a bug.