Heard of the Stanford Prison Experiment? About half the book covers that landmark study in a cinematic and engaging way. The last half of the book is the real deal, though. Zimbardo introduces you to his theories of situational influences and applies these theories to what happens in places like Abu Ghraib and Guantanamo (it's seriously scary, 'cause last night on the news, I saw that they're trying to transfer a lot of the prisoners in "Gitmo" to other countries - a practice that Zimbardo exposes in this book too). You'll discover that patriotism can be an ugly thing as you read the Abu Ghraib chapters.
This book will change your life. At the very least, your way of thought. You'll second-guess your own ethics, intentions and independence. You'll scoff a little, make fun of Zimbardo's self-exonerations. Then you'll really start reading and you'll find that maybe you won't be the hero you need to be when the time comes.
Everyone should read this book.