> There are a lot of e-book reader with a built-in backlight that can be turned on and off, like the Kindle Paperwhite.

"Paperwhite guides light toward the surface of the display with its built-in front light—unlike back-lit tablets that shine in your eyes" [1]

I have a Kindle Paperwhite, and was surprised to read this article, because I have no trouble sleeping. Apparently the way the light works is the reason for this :)

[1] http://www.amazon.com/Kindle-Paperwhite-Ereader/dp/B00AWH595...