Thaler, R. H., & Sunstein, C. R. (2008). Nudge: Improving Decisions About Health, Wealth, and Happiness. New Haven, CT: Yale University Press.
Here is the blurb I wrote for the back cover of this book (it got edited a bit, so the actual blurb is shorter.)
This is a great book: engaging, informative, and thoroughly delightful. Imagine: deep thoughts in an easy read, with social and legislative suggestions to improve everyone's well being through a constructive, non-coercive (libertarian) social policy. It doesn't matter whether your politics are left or right, up or down: Thaler and Sunstein provide important lessons for structuring social policies so that people still have complete choice, but are gently nudged to do what they wish to do. Well done.
I stand by the review: This is an important book for researchers, designers, and perhaps most of all, those who must implement social policy. Rich Thaler and Cass Sunstein's original title was supposed to be "libertarian paternalism," but fortunately reason struck and they discarded it. But they tried out that title because it does reflect the underlying principle of the boo. How can we get people to do what is best for themselves (such as to take out health care or save for retirement) - this is the paternalism voice - yet without forcing them and still giving people the choice to do as they wish - this is the libertarian voice. Note that standing back and doing nothing is not an option. The environment is always rigged so as to nudge people towards one choice or another, so as long as that is true, why not nudge in the most beneficial direction?
The principles apply in a amazing variety of situations. The power of gentle nudges.