I think Bryan Peterson is pretty great, and has one of the best books on understanding exposure. He explains exposure – talks about Aperture, Shutter Speed, ISO, Light and special techniques and filters.
What I liked most about the books is the examples and the way he explains exposure. When you’re first trying to understand how your camera works, words like ISO and Aperture don’t mean a thing, but he explains it in a way that makes sense. For instance here is a quote when he explains ISo
“To better understand the effect of ISO on exposure, think of the ISO as a worker bee. If my camera is set for ISO 100, I have, in effect, 100 worker bees; and if your camera is set for ISO 200, you have 200 worker bees. The job of these worker bees is to gather the light that comes through the lens and make an image. If both of us set our lenses at the same aperture of f/5.6 meaning that the same volume of light will be coming through our lenses – who will record the image the quickest, you or me? You will since you have twice as many worker bees at ISO 200 than I do at ISO 100″
He also has an updated version to the one I own – Understanding Exposure the 3rd edition that you might want to check out!