The new Kindles (Paperwhite, Voyage) are backlit. If that trend spreads to other e-readers it won't just be a tablet problem. I guess this is a good argument to keep the old style Kindles around.
This article on what I assume was the same study http://arstechnica.com/science/2014/12/e-readers-and-tablets... mentions specifically "iPads, Kindle Fires, and Nook Colors", and also says "A Kindle without a backlight, as you'd expect, only reflected about as much light as a book and had its peak omission in relatively red wavelengths."
"Paperwhite guides light toward the surface of the display with its built-in front light—unlike back-lit tablets that shine in your eyes—so you can read comfortably without eyestrain."
Source: http://www.amazon.com/Kindle-Paperwhite-Ereader/dp/B00AWH595...
Illustration: http://www.nytimes.com/interactive/2012/12/26/technology/lig...