To calculate the overall star rating and percentage breakdown by star, we don’t use a simple average. Instead, our system considers things like how recent a review is and if the reviewer bought the item on Amazon. It also analyses reviews to verify trustworthiness.
When I recieved this book that I purchased for my son I was surprised to see that it was bound upside down,ie the cover was the opposite way round from the pages so the words and pictures were upside down! Very unproffesional!