Understand what a book review is. A book review is a critical analysis of an author's work, taking into account what the author has tried to do and how well they have managed to do it, in your opinion. It should evaluate the quality, meaning and significance of the book and it should provide a description of what the book is about.
Analyze the book. Understand what the book is about. Look at the themes it explores, as well as the characters, plot, style and setting. Think about what message the author is trying to portray. If there's an introduction, preface, or forward, read it to see if the author mentions their inspiration or thoughts about the book.
Evaluate each point you make. Always back up your points with evidence. When you are writing a formal book review, it is not enough to just put across your opinion--you must explain the reasons for your opinion. If you think the plot or message is not relevant to a modern audience, don't just say it, evaluate why it is not relevant. Ask questions that will help you to assess the quality of the book.
Explain your evaluation. Link your chosen pieces of evaluation to specific aspects of the book and convince the reader by using solid examples.
Carefully read and summarize the text. For you to be able to provide a fair and accurate evaluation of the book, you will need to read it first. As you read the book, keep a note book or piece of paper next to you; note and summarize key points you come across while you are reading. These points may include parts in which the book excels and parts where it falls shorts. This will help you to decide which points you want to include in your review.
Don't use a conversational tone full of slang or informal expressions. Stay on the topic; read your analysis and edit your work it stays focused on the book you're reviewing. Avoid insulting or offensive terms--you do not want to come across as aggressive in your writing. Make it clear that you're well-informed, that your criticisms are justified and that you can express them fairly.