I highly recommend "Ultralight Backpackin' Tips" by Mike Clelland. It is both entertaining and educational. It is probably best for people who have some backpacking experience, but want to reduce pack weight. At first I was a bit put off by the illustrations / cartoons, but they really contribute to the light-hearted style.

It is a quick read, but it manages to combine the "big picture" with lots of specific suggestions. I love his attitude that ultralight does not have to be expensive, like a DIY alcohol stove or razor blade knife. It really opened my eyes to what I *don't* need to take with me, like extra clothes or a "footprint" for under my tent. It also encouraged me to modify my gear - I cut off excess pockets, zippers, and straps from my backpack which reduced its weight by over 30%.