A book review is a form of literary criticism in which a book is analyzed based on content, style, and merit. It is often carried out in periodicals, as school work, or online. Its length may vary from a single paragraph to a substantial essay. Such a review often contains evaluations of the book on the basis of personal taste. Reviewers, in literary periodicals, often use the occasion of a book review for a display of learning or to promulgate their own ideas on the topic of a fiction or non-fiction work. At the other end of the spectrum, some book reviews resemble simple plot summaries.