Instruct: Classify a review into positive or negative sentiment.
Query: This book is purely a vehicle to sell products.

This book is nothing more than a vehicle to sell the authors soy protein drink. You cannot be on this diet without using his products. His soy protein powder is alll you consume while on this diet (along with vegetable broth). At $29.00 a can, it is not cheap. Average consumption is one can every 7-10 days. The Atkins diet is a much better vehicle for serious weight loss.