Never discussion

Why do reviewers virually rewrite the book they are reviewing and turn it into a short story ? Some reviews are so long and detailed. There may not be a "spoiler"warning, but the retelling of the story still takes away much of the pleasure of discovery for a reader. I buy books for a community library and I do check on reviews for titles I may purchase, to see what audience it may appeal to. I try not to read reviews of books that I want to read, because prior knowledge ruins the enjoyment. (as it did for Never)