You basically want to make note of important details from the book and give your opinion about those important details. Let's say you're reviewing some makeup. You'll try out the makeup, tell what the company or that typical makeup is trying to give you (clear skin, matte skin, long-lasting, etc.), then you want to tell what you think about the product (this foundation helped was lightweight and lasted all day, but made my skin very oily and caused me to break out).
Hope this helps! You can also just type into Google "Book review examples".
