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.
The book is standard Walliams but personally I found it really boring to read to my child and thought writing was a bit lazy and rehashed from previous work. However, my son liked most of it so I think a 3 star is fair.