The Omnivore's Dilemma by Michael Pollan
WARNING: This book will make you think.
A natural history of four meals.
In this award winning book Mr. Pollan traces four meals through their food chains. It's an in depth study of where food comes from and what happens to it along the way. This book will not attempt to convince you to become a vegetarian; it revolves around the seemingly simple question "What's for dinner?".
Everyone who eats should read this book.