Amazon calculates a product’s star ratings using a machine learned model instead of a raw data average. The machine learned model takes into account factors including: the age of a review, helpfulness votes by customers and whether the reviews are from verified purchases.
Fantastic take on the apocalyptic fiction, insightful, interesting, so well written and the way the author goes from before in one chapter to after in the next just makes such imaginative reading. And the ending, well, it blew me away. Read and enjoy people, just read and enjoy.