I just saw a three-star review on one of my books (which I consider low). The only comment: “Still reading it.” The person hadn’t even finished the book!
Another reviewer gave another of my books a brutal one-star review, saying it had fewer than 100 pages. The book is actually 176 pages.
I don’t mind tough reviews. I’ve given a few myself. But before you downgrade an author’s hard work and hurt him financially, is it too much to ask that you actually read the book?