Really good book. Author gathered stories and scientific data that covers all aspects of habits. If you have bad habit or you want a new one this book can really help, especially by explaining what works, and what not.
tldr; rating 9/10 fun to read and I have learnt a lot about habits.
First author explains how habits work, why they exists? They are really useful most of the time as you probably know but there is more than you might think. The best thing about habits is that they are not using willpower. Please read more about how willpower is important here: http://oliveremberton.com/2014/life-is-a-game-this-is-your-strategy-guide/. It's really our most important asset so using habits to get the job done and at the same time not use willpower is a great thing about habits!
Above is true of course if you have a good habit, unfortunately not all habits are like that :/ Turns out that most of our habits are pretty hard to get rid of. You need to be conscious about what you doing and spent great deal of willpower to stop bad habit. Fortunately many people have done that before, think about AA, habits are connected to addictions so while fighting with bad habit it's good to know what to do. One unexpected thing that I learn is how to deal with crisis, I have seen many people give up when crisis come. I myself many times fall trying to create new habit or get rid of something at this point.
The end of book is a nice todo list how to deal with habits in your own life. At least you know what to do exactly to master your habits :)