Amazon calculates a product’s star ratings based on a machine learned model instead of a raw data average. The model takes into account factors including the age of a rating, whether the ratings are from verified purchasers, and factors that establish reviewer trustworthiness.
Finally I can buy Chinese kindle book from amazon! The author is someone I highly respect. I admire he can still stay positive while he was fighting with cancer. This book is a good reminder for all of us that life is short, make sure you dont waste it.