The overarching argument of the book is animal-based diets lead to more chronicle diseases than plant-based diets. The method of study is statistical. Just as I believe smoking leads to lung cancers and physical exercises are good for health, I agree that vegetarian-style diets are probably healthier.
However, the structure of the book tends to be misleading. The author starts successfully by convincing me with solid statistics that plant-based diets are probably a good choice. Then, the author chooses to argue that there is a commercial conspiracy behind animal-based diets and scientific reductionism should not count in nutrition study. I have reservation for both of his arguments.
First, I agree that commercials can mislead people, but I think rational people are aware of the truth. For myself, I probably will continue my meat-based diets even if I know this may contribute to chronicle diseases, simply because health is not the exclusive consideration when I make a choice of diets. The commercials may be catering to me in terms of diets, but they are not the reasons why I make a choice of meat-based diets.
Also, as I become aware of the problems with animal-based proteins, I'm conscious of the risks of chronicle diseases. Then, I want to digest some supplements for my health, and then comes the commercials. In others words, it's because I have this demand that there is such a market, not that there is a such market that I fall into such habits.
Adding to the above arguments, I want to defend for scientific reductionism. Scientific reductionism means to isolate those individual factors that contribute to certain phenomena, and thus build a causation between cause and effect. Arguably, contemporary literature are not able to provide a clear-cut proof that lack of or over-taking certain nutrients are causes of certain chronicle diseases, as it's currently impossible to do control experiments over such a long period of time. However, this current impossibility is insufficient to argue that scientific redunctionism is redundant in nutrition science. As I argue above, we have a meat-based diets because we want it. If we want to shield against chronicle diseases at the same time, we have to know by add what can we reduce the possibility of having chronicle diseases.
Or in other words, we want to separate diets from health to some degree. How to still be healthy when the delicious is not the healthy? This should be the topic for nutrition scientists, rather than the other way around.
As a summary for my opinion of this book, I'd like to say, I agree that plant-based diets are healthier than meat-based diets, but my diets are still under my control.