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.
Arrived without any problems, book has great colors and thick pages. I especially like the feel of the hardcover. The book is great, I use it for my first neuroscience class. It's full of useful information and helpful extras. It's a great book, but not a magical book - ultimately, you still have to study for the exams. :D