Amazon calculates a product’s star ratings based on a machine learned model instead of a raw data average. The model takes into account factors including the age of a rating, whether the ratings are from verified purchasers, and factors that establish reviewer trustworthiness.
My 5 year old loves these books and loves astronauts so I thought this one would be a win win for us. He loves it, but I'm not crazy about how this one was written. He's happy so I'm giving it 4 stars.