The world is created by an author and the book is bought off Amazon. When the book is finished, Amazon prompts for a review. There’s a moment of self doubt about writing a review for the book. Many times this self doubt rules and the review is never written.
Before that happens, please consider the benefits of such a review.
Amazon promotes, ranks, and values reviews on books. Authors get a boost on multiple reviews. Sometimes they help with small ads if the book gets notable.
Author’s watch their reviews. They use the statistics as credibility for their work. Many authors also use the feedback in order to improve their craft. Sometimes the monitoring of their reviews deter them from writing something else for fear nobody read their work or felt their words were valuable.
Good or bad, a review helps those who sell on Amazon. Take that opportunity and boost the author by posting a review!