Decide on your primary objective for the book report. Professional book reports and reviews are written for a variety of reasons, but it is possible to break down professional book reports and reviews into two categories: a summary of the author and book, and a critical review. The purpose of the first category is to present an overall summary of the book, a commentary on subject matter and writing style, and a few remarks about how it relates to similar books. A critical review typically uses the book as a point of reference to develop an opposite point of view or perspective. For example, academics may review books by colleagues to point out the mistakes and develop a counter position.
Write for a particular audience or group. Keep in mind who the book report is being written for. If you are writing for a professional group of colleagues or peers, the book report may require a certain style of academic language suitable for the academic context being addressed. At the same time, certain bits of knowledge can be taken for granted and don't need to be explained to the reader. If you are writing for a more general and non-academic audience, a less specialized vocabulary and writing style are more suitable to getting your points across.
Make an outline of the subject matter and content for a non-fiction book. The outline may include the major topic and theme of the review; an analysis of the book's content; a consideration of the language, symbolism, structure, or methodology of the book; an evaluation of the author and his place within the genre; and an overall evaluation of the book. Outline your arguments if you are writing a critical review. In what ways do you agree or disagree with the author? What do you think the significant contributions of the book are? What points do the book fail to address or wrongly address?
Make an outline of the essential elements for a novel, play or collection of short stories. A book report or review for a work of fiction needs to take the content and style of the storytelling into consideration. Focus on the setting, the time period, the characters, and the plot. An interesting report will critically analyze the author's writing style and technique. It is helpful for the reader to know something about the author.
Write the report or review. Always start with an attention-grabbing opening sentence and introductory paragraph. The introductory paragraph should set the overall tone. The main body of the article should address each of the individual points. Conclude the report with an overall evaluation of the book and your own personal view about the substance of the book.