E-readers are a good investment if you spend a lot of time reading e-books. With a long battery life, e-readers are also lighter than tablets and the text on screen does not get washed out under sunlight.
However, the E-Ink screens used in e-readers are not backlit, and thus cannot be read in dark rooms. Barnes & Noble aim to solve this problem with the Nook Simple Touch with GlowLight. It's basically a Nook Simple Touch with LED lights along the edge of the screen which light up for reading in the dark.
The brightness can be adjusted, and Barnes & Noble have stated that the Simple Touch with GlowLight can go for two months before running out of juice if you don't use the light at all. It can still last a month on a single charge if you use the light for half an hour daily. Available for pre-order now at US$139, and will ship in early May.