The Omnivore's Dilemma, by Michael Pollan
Michael Pollan traces four different food chains: the industrial, the sometimes-not-so-organic organic chain, the self-sustaining farm, and the hunter-gatherer lifestyle. He experiences each one, going so far as to buy his own cow for slaughter, hunting his own wild pig, and working the farm daily. I found this book so fascinating. It's so easy to eat and not think about where your food came from, and it's great to read someone's own journey to answer their questions.