Alchemy by Rory Sutherland
8 out of 10

If you are always logical, you are predictable, and therefore, hackable and exploitable.  Discussing game theory and evolutionary psychology, Sutherland makes a convincing case for the necessity of illogical behavior.

"The trouble with market research is that people don't think what they feel, they don't say what they think and they don't do what they say."  --David Olglby 

Creative experimentation never turned lead into gold, but it has created some unexpected gems in the business world.