Punished by Rewards: The Trouble with Gold Stars, Incentive Plans, A's, Praise, and Other Bribes This is a classic. Anything by Kohn is a start for rethinking schools.
Why We Do What We Do: Understanding Self-Motivation Deci is my all-time favorite researcher on motivation
The Lucifer Effect: Understanding How Good People Turn Evil Zimbardo always exposes those parts of humanity we may not want to admit to.
The How of Happiness: A New Approach to Getting the Life You Want Sonja is a great researcher in this field!