I have his book. It was recommended by one of my doctors(environmental/allergy). I have IBS so for me it's not that simple.
His diet is basically a low calorie diet consisting of mostly vegetables(low carb/starch). So of course you are going to lose weight. He uses the bulk fullness effect from eating vegetables and salads. In other diets including meat/fat they depend of the siety factor of the foods.
He makes a lot of claims, but I don't think they are justified. He main supporting argument is the China study or at least an interpretation of it.
For me there is nothing new here. Many people have done similar studies and have come to different conclusions. If nothing else the diet should inspire you to steer away from processed commercial foods and into more fresh vegetables and greens.
Every person is different. Adjust your diet accordingly.