If you are ever in a position where you need to motivate people who do more than redundant physical tasks and you are using the carrot and stick approach, you suck at your job.
People want to feel like they are a contributing factor and have purpose, they want to be able to hone master the skills they enjoy, and they want to the ability to have control over how they do that.
Purpose, Mastery, Autonomy. These are the staples of productivity in a work place that requires more than just physical redundancy. This book sheds light on how we have been trained to use only reward/punishment vectors to control people and then wonder why we can't really get people to engage.
I have seen the ideas in this book applied, I have applied it myself. It works.
If you want a teaser into his book, here is his Ted talk and he is a fantastic speaker.