Some readers (such as the upper level Sony model, the 700) have lights built in. They're not backlights, but they illuminate the screen for you. Others don't have them built in, but have small led light accessories you can buy. So yes, you can read in the dark.

The catch is that powering a constant light source drains the battery much more quickly. Your battery life will once again be measured in hours (albeit quite a few hours), rather than days or weeks. That's probably not a big deal for reading in bed though, since you'd be right by a power outlet.

Here's a picture of the 700 I was talking about. The picture is a bit blurry, but rest assured that in real life, the lights look nice, and the screen is crisp.