I think this is an excellent book, having read it already twice. There are many approaches to low-carb, but their book is one of the best I've read on the subject.
First and foremost their book is concerned with healthy living and they go to great lengths to explain and show what "healthy" is supposed to mean. They answer all the "why" questions you have. And they do this well. They may be a bit doctoresque and too scientific in their approach, and that may be a turn off for some. However, if you really want to know what you're doing and why, this is the kind of knowledge you must assimilate.
For the most part their book is balanced, and it's lovely that it has three levels om commitment: called Hedonist, Dilettante and Purist. The first is essentially Atkins, Dilettante is more restricted and tries to eliminate some low-carb foods that simply aren't healthy no matter how you look at it. The Purist approach is the same as the Neanderthin/Paleo diet, only with the carb counting.
Others have done a better job at showing the historical background for the current dietary advice of low-fat/high-carb cures, but that's only a small criticism. Some would say it's a more scientific book than motivational, but that may depend on your temperament. But I kinda like their approach: for once they don't talk so damn much about "will power" and that whole Fat Club thing about commitment. I think that's cool, because one week after you begin their diet you'll realize that it doesn't take ANY will power to make it succesfully. The fact that you can eat good food when hungry, and that you get your blood sugar under control, will _give_ you the will power for free.
My heart lies mostly with the Neanderthin/Paleo diet, but I like this book for all the above reasons and because the Eadeses actually use that evolutionary perspective to structure their whole approach - despite allowing a lot of non-paleo foods. They just realize that we're just humans and have to have some fun once in a while.
If you're going to low-carb, buy this book.