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.
This worked on my older 6th gen Kindle Paperwhite, and I would read this book to my little girl at night. I just purchase a 9th gen Kindle Oasis, and it is not compatible with the newer e-reader. I am very disappointed.