If you’re not careful, leaving reviews, good and bad, on Amazon and Goodreads can make you the subject of an attack from trolls. Don’t forget that you might have liked a book that others believed was dreadful. So, writers that have been at this game for many years don’t recommend leaving reviews of any kind. Instead, if you want to show your support for other authors, help spread the word. Share links on Twitter, Facebook, and other social media. Recommend the book to others in your discussion groups. Tell your readers about the book, either directly on your blog or through your email list. Utilizing your contacts to help another writer promote their book is probably the best way to show them how much you enjoyed their book.
Remember, it’s about protecting yourself and your reputation. Don’t give the trolls a reason to attack.