Duhigg’s one big idea in the book is that our habits can be broken down into three factors: A cue that triggers the habit, a routine that we subconsciously follow, and a reward that motivates us. He contends that we can’t eliminate a bad habit, but we can change it by inserting a new routine between the cue and the reward. That’s a deceptively simple, but very powerful, idea.
Duhigg also describes the power of “keystone habits”, which can trigger many other habit changes. For example, for many people, getting fitter is a keystone habit, which leads to them adopting other unrelated positive habits as well.
If you’re looking for practical steps to change your habits, jump straight to the Appendix, which is a “how to” of the entire process.
I love that the book is backed by strong scientific research (the references take up a full third of the book). But Duhigg is a Pulitzer prize-winning journalist, so his writing is compelling and entertaining rather than dry and academic.