Customer Reviews, including Product Star Ratings help customers to learn more about the product and decide whether it is the right product for them.
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 analyzed reviews to verify trustworthiness.
I'm still in the middle of reading this book, but up till now I have found it a very enjoyable read. I happen to work with the author in Japan and this is the first time I've ever bought one of his books. I will certainly be buying more of them.