At times I come across a book review where the reviewer is doing it wrong. Oh, you might ask, how can a book review be wrong? After all, a review is highly personal, nobody can tell me how I write my review?
True, in the end it is up to the reviewer. However, there are a few things that would be good to keep in mind.
Perhaps the most important one: don’t spoil the entire story. No matter how enthused you are about the book, it is not in good taste if you give away the entire plot. That takes away the entire fun or excitement for readers who have yet to start the book.
Don’t say you disliked the book without telling why. Your reasons are what make your opinions interesting.
If you feel something is wrong with the book that has nothing to do with the story (for instance the formatting, the spelling or the editing), don’t put that as the most important issue in a review. Reviews are not for these things. In that case see if you can get in touch with the author. Most authors have a website with a contact-link, many of them are on Facebook or on other social media.
If you stick to these simple things, I am sure that your reviews will be most helpful to the author and other readers.