Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Nutrition book written by an authentic expert

The majority of books written on nutrition are written by people who have no credentials. Willett is a respected Harvard Professor. He also writes articles in peer reviewed journals. Much of this book is based on Willett;s own research. The book is short, well written, and easy to read.I learned a lot from it. It has much useful information on nutrition.