I think it also matters how you interact with said content. Scrolling is really bad as it needs near constant interaction but page turning via taps anywhere on the screen seems to work really well.

The screen on my eReader is a way better shape than any phone when it comes to reading books. Add to that the fact they cost a fraction what a phone costs and can't possibly send a notification to keep you awake makes them the superior falling asleep device for me. I also don't need any weird hacks like this to make the screen really dim.