I'm a professional who works with autistic kids, and I can tell you from experience that what works for one child will not necessarily work for another. Some children improve so dramatically with this diet, and especially with this diet and the drug nystatin, that I encourage all curious parents to try it. However, don't invest all your hopes in it, or stop other therapies, whether they be ABA, or anti-anxiety medications, when you try the diet.
Autistic behaviors as well as degree of expression fall across such a wide spectrum, that I have always believed no one single cause would ever be found. I believe however, that this diet, and the theory of casiomorphins, glutomorphins, and yeast overgrowth, is the answer to one type of autism.
This diet, and its history of discovery by persistent parents, is no less than another tale of Lorenzo's Oil.
The only drawback to this book is Lewis' personal story. She talks in such vague terms of her son's behaviors and "improvements," that the reader has no picture of what is happening, and whether it's dramatic enough really to credit the diet.
However, the diet, the recipes, the resources are brilliantly presented. Everything a parent needs to start and maintain the diet is here. You won't find yourself, wondering, doubting, or second guessing, because the coverage of the actual diet is quite clear and complete. I wish there were some kind of Pulitzer for reference books, because I would nominate this one.