You should judge as far as you can reliably do so, and leave the final evaluation of your review to the reader. Expository writing has become a very well understood form of communication. You can learn to write clearly, compactly and forcefully without possessing any literary talent. The passive voice should never be used. Do not put statements in the negative form.
Verbs have to agree with their subjects.
Proofread carefully to see if you words out. If you reread your work, you can find on rereading a great deal of repetition can be avoided by rereading and editing. A writer must not shift your point of view. And don't start a sentence with a conjunction. Place pronouns as close as possible, especially in long sentences, as of 10 or more words, to their antecedents.