A book review is a summary, critical analysis, and an evaluation on the quality, meaning, and significance of a book, not a retelling. It should focus on the book's purpose, content, and authority. A critical book review is not a book report or a summary. It is a reaction paper in which strengths and weaknesses of the material are analyzed. It should include a statement of what the author has tried to do, evaluates how well (in the opinion of the reviewer) the author has succeeded, and presents evidence to support this evaluation.
There is no right way to write a book review. Book reviews are highly personal and reflect the opinions of the reviewer. A review can be as short as 50-100 words, or as long as 1500 words, depending on the purpose of the review. http://www.lavc.edu/Library/bookreview.htm