The book Nudge exposes aspects of current behavioral economics research and make suggestions on how they might help solve current issues, especially in public policy. The research is fascinating, the insights are interesting but it's all presented in a "dumbed down", "pop science" package - perhaps trying a bit too hard to appeal to the masses. And the writing is all but concise.. too bad.
I would recommend reading Thinking, Fast and Slow (by Daniel Kanhemann) before Nudge. It has a more systematic and intellectual approach and is written by the father of Behavioral Economics