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.
I would recommended this book to anyone who is a beginner. It shows you a step by step instruction which is very helpful,my mother was amazed when I showed her my drawings. This book also teaches you how to draw very difficult animals in very easy steps. I never expected such a nice book.