Don't read it. Don't buy it. Don't borrow it. Don't waste your time.
There are a bunch of really weird and disturbing things about this book, like the chapter about Rosa Parks that focuses on loose ties and doesn't really correctly frame Parks as the activist that she consciously was -- and then interleaves it with stuff about Warren and Saddleback (so, so, so wrong!!!) that ignore the multi-generational preacher aspects of the Warren family. There's a bit about gay rights:
"For example, when gay rights organizations started campaigning against homophobia in the late 1960s, their initial efforts yielded only a string of failures. They pushed to repeal laws used to prosecute gays and were roundly defeated in state legislatures." Conveniently failing to note the successes in municipalities in California that inspired Stonewall, and a variety of legal victories around the same time. "Then, in the early 1970s, the American Library Associations Task Force on Gay Liberation decided to focus on one modest goal: convincing the Library of Congress to reclassify books about the gay liberation movement... the Library of Congress agreed ... the effect was electrifying ... Within a few years, openly gay politicians were running for political office in California, New York, Massachusetts, and Oregon".
So, yay, ALA, but this misrepresents the timeline in so many ways it is hard to know where to begin, much less end.
Like many business writers, Duhigg is a lot more attached to "good stories" than he is to accurately describing reality, which is unfortunate, because we usually learn the most from those points where reality fails to follow the well-trod path of a "good story". Also as is typical of business writers, he tends to find "successes" and then go back and ask them what they did, and then (a) assume their recollections are accurate and (b) because success happened after what they claimed they did, the success was the result of what they did. Two problems there: people often remember the past somewhat if not entirely inaccurately (yes, I always turned my homework in and on time and done carefully!) and are there people who started out the same way but wound up in a much less good place? Un-confirmed anecdotes plus a logical fallacy leads one directly into the self-reinforcing land of We Must Be Good and Moral and Chosen Because We Are Rich and Famous error, a classic of the smugly self-satisfied who firmly implant their fingers in their ears and shout I Can't Hear You! whenever someone tries to say, but I did everything right, how come I'm unemployed and losing my home? Etc.
Also, his advice on habit modification is soooooo bad -- he seems to think AA is really effective. *sigh*
Habits are important. Everything we do, we do on autopilot -- including a lot of how we (re)program our autopilots, which is sort of a problem for people who could use a meta-level habit tune-up. I was really hoping to read a book that developed and expanded upon that idea. This is not that book.
In an ongoing effort to find that book, I am now reading Prochaska et al's _Changing for Good_, mentioned by writers like Miriam Nelson (I like Miriam Nelson's work. It is the good kind of simple.). It has its own problems, but it's way better than Duhigg.
Weirdly, along the way I've stumbled across a bunch of stuff about managing bipolar disorder by stabilizing life routines (mostly Ellen Frank's work developing IPSRT, if you want something to google -- she writes books for clinicians and I'm not necessarily interested enough to read http://www.amazon.com/Treating-Bipolar-Disorder-Individualized-Evidence-Based-ebook/dp/B003TXT08I, but maybe you are). This isn't _instead_ of medication, it's complementary treatment (generally speaking, anyway).
I also picked up Cohen and deBenedet's _The Art of Roughhousing_, which is really great. I mean, _really_ great. Nothing quite like reading a parenting book with lists of What To Do and What Not To Do and nodding as you go along, because everything is familiar -- except, oooh, cool new idea! I'm not done with it yet, and am sort of hoping they get around to talking about kids and martial arts at some point, because the connections are really obvious, at least to me.