A lot of research has been coming up about how exposure to/use of devices such as laptops, tablets, and ipads right before bed can disrupt you ability to fall asleep. This has to do with backlighting and blue light. So what about ereaders like the Kindle?
Here is a list of links suggesting the most kindles are front-lit, and therefore not distuptive
http://gizmodo.com/5524005/experts-kindle-helps-you-sleep-ipad-causes-insomnia
http://www.tomsguide.com/us/ipad-kindle-sleep-cycle-ereader-lcd,news-6586.html
However the Kindle Fire IS backlit
http://science.opposingviews.com/kindles-backlit-18332.html
Sleepshield makes a blue light filter for various devices:
http://www.amazon.com/SleepShield-iPhone-Blue-Light-Filter/dp/B00FVROX46#
http://www.amazon.com/SleepShield-iPad-Blue-Light-Filter/dp/B00ILZCTH8
And here is a review of which night lights are less likely to disrupt sleep