First. Analyze what kind of book it is. What genre was it? What was it like, what made it stand out compared to others of the same kind, what aspects of the novel stood out: Example: In what way was the story told?, what was the language like, was the author good at describing people, environments, animals, details, characters, their mindsets, men/women/children?

What is the premise of the novel? Give as much on the novels story as you think is necessary to make the reader grasp what this novel is about, but without spoling anything vital to the plot or accidentally give the ending away. This section of the reviews should be as short as possible. A review is not supposed to be a recap of the story, because then it would be only that and there would be little reason to read it. And readers would be angry for having everything spoiled.

Did the story flow? or was it hard to read? did it have any obvious bottlenecks which in your opinion were boring/hard to understand/filling material etc. Wether it was good/bad-Always explain why you think so!

You can if you want include a small quote from the book that you think is representative of either the authors skills at describing, or shows what the language is like.

You can of course tell readers if you liked/disliked the novel but you have to tell on what grounds you thought it bad/good.
Like this for example:
"I thought this novel was an intriguing read because the way the author described the relationship between the man and the bear showed that if we want we can accomplish greater understanding between humans and animals and find we are not so different after all."

Hope this is any help..