This exploration of the hidden side of everything has some excellent tales that force you not to assume the obvious - the corrleation of factors and direction of causality is what economics is all about and this book uses those powerful tools to better understand some interesting social phenomena.
There's lots of good stuff here but the book is founded on a few key principles:
Incentives are the cornerstone of modern life - an understanding of incentives, both positive and negative, is the key to understanding human behaviour
The conventional wisdom is often wrong - it's often used without any substantiation because it's comfortable and easily swallowed
Dramatic effects often have distant, even subtle causes - the answer to any given riddle is not always right in front of you