I have a Kindle. Kindle is proprietary which means you have to purchase books from Amazon - or convert books purchased from Barnes & Nobel through a free online site called Calibre. I have not used Calibre yet so I can't say if it is easy or hard or if it even works. Books are priced about the same on Amazon as at Barnes & Nobel. There are thousands of free books available too that will load on to Kindle. You can get thousands of 'classics' at gutenberg.com for any e-reader you purchase. Keep in mind if you purchase a Nook or another brand, you may not be able to down load books from Amazon.
Having an e-reader that is back lit (like a computer screen) makes it easier to read in bed, but the bright light may actually keep you awake longer. There are lights that will clip on to your e-reader making it much more like reading a printed page.
If you can go to Barnes & Nobel and look at what they have, it might help you decide. Do your research to find what features you might like and who has the best price. Good luck and enjoy your new e-reader.