I have just finished reading Understanding Exposure by Bryan Peterson. It was a pretty good book. Nothing earth shattering in it. There are some good tips on how to set aperture and shutter speed for different shooting conditions. It was definately written in the era of film, when DSLR’s were not really an option. He pushes using manual mode, and setting both aperture and shutter speed your self. Nothing wrong with that, but it seems like the built in light meters are better now. My D40, and now D90 do a good job in most situations. I prefer to shoot in aperture priority, or shutter priority and have the camera set the other. With digital I can then chimp the screen, and then adjust the exposure override. That just makes sense to me. I suppose that going the manual route would push understanding of exactly what is happening light wise. Maybe.
Anyway, I would recomend this to a beginner especially, and as a good “oh yea, I forgot that” type of read for those that are a little more advanced. It is not very expensive. I picked up mine with a Borders coupon a few days ago.