How some books on Amazon get 5 stars is beyond me, perhaps it is from people who are easily entertained or even easily educated (which then doesn't say much about much).
This is a very simplistic book and here it is in a nutshell : Small habits done daily compound and add up. In other words if you eat cake today, no big deal, if you eat cake everyday you're on your way to bad health. Wow that was earth shattering knowledge. Then it goes on to describe how to get rid of bad habits: one, try to make it hard for you to do them and to implement good habits try to make it easy for you to do them. And then each chapter will give you an idea of how to make it easy. Eg. Make it easy by your environment, ie. keep your gym shoes near your bed.....(wow such wisdom.....lol). Have friends who are similar minded to your habits, ie. you both like going to the gym etc.
Each chapter starts off with a short story about something connected to the habit discussed, which I find is a cheap way for an author to look "intellectual". Eg, back in 1942 some Russians did experiments on bladdy blah .
I suspect the 5 stars are because its an easy read. I suspect the 1 stars are because 3 months after reading the book you won't change a darn thing and you'll continue to live your life like you always have. Therefore the book is worthless except for a bit of entertainment.