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 got the book in time, and though I got it quite some time before, I am just starting to read it and looks like a good book for kids/idle reading. Simple words, simple story. After all, I think the main focus of the famous five series are the early teens. I am a doddering ole man but sometimes I like reading kids' books and this one is certainly a kid's book. And yeah, written by Enid Blyton.