Learning how to write a book review is a useful technique to have, whether you're a student, a beginner blogger, or just someone who wants to use Goodreads more frequently! Given the setting, this is definitely the best approach to start any evaluation. However, be careful not to divulge into much information. Many review sites explicitly encourage star ratings, but they are not required. If you do decide to rate something, you can use the standard "out of seven/ten" scale. You might also try categorising your star rating in order to do something a little less typical.