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.
My kids that I work with as a speech/language pathologist love this book. It's funny with the requirement (for me) to have lots of repetition. I've used several of the Old Lady books because they are so fun!