The base model Kindle ($79.99) doesn't have a light! That said, the Kindles with lights don't have backlights, they're frontlights, in that the lights are pointed down onto the Kindle's screen rather than up into one's eyes; this is why Kindles (and other eReaders) generally don't cause eyestrain the way iPads/tablets can (or, at least, not to the same degree). Also, you can turn the light down almost all the way. It never technically turns off, but at in my dark bedroom at night I don't see any light if I turn it down to 1, and you're supposed to turn the light down in darker environments and up in brighter ones.

But yes, there is a model without a light at all.