Recommended reading for understanding Nikon CLS

i've been using a D300 for four years (a D200 for a few years before that and a D70 for a few years before that) and have four Nikon Speedlights. I understand how to set them up wirelessly and make it all work, but i want a deeper understanding of the impact of aperture, shutter speed, synch speed, TTL vs manual vs. TTL-B, etc.

Can anyone recommend some good reading material? i've read mos of Joe McNally's books, which i enjoy, but i'd like something a little more instructional and explanatory