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.
DO NOT BUY photos advertising product are very misleading as the shelves are actually too small to fit any average sized books on. You would need to have only very small books in order for them to fit. Not fit for purpose, extremely disappointed and let down.