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.
It’s just not that good… looks like an article from his website. And the bar is just to damn high on the other one. Diversify, and maybe even try Mark Manson’s recommendations of books, they’re really good.