Catherine Jayne,

The Kindle (and I think the Sony eReader as well) uses something called eInk. It feels different from looking at a computer screen, and is very comfortable on the eyes for lengthy reading.

The Kindle, by the way, does not have any built in light. For use in low light situations, you need to use a booklight as you would with a paper book. I believe the SONY eReader does have some kind of lighting, but I could be wrong on that.