My new Kindle Fire (Black) does have an automatic shut off if no activity has been detected (page turning or advancement) if I fall asleep while reading.
I love that feature as I sometimes read my Kindle Fire in bed.
Backlight can be dimmed down and background color can be changed to lessen the glare on your eyes.
I liked changing the background color to black and having white lettering the best - especially to reduce the excessive glare on my eyes from looking at a white background for a long time.