Prepare to write your summary by taking notes as you read. The Purdue Online Writing Lab gives suggestions on this initial step, saying to pay special attention to what kinds of characters the book features, the main ideas presented and memorable quotes from the text.
Using the notes you have made, summarize the book in your own words. The main mistake people make when writing a summary is trying to tell too much; give an overview without giving every detail.
Look for examples of book summaries to use as guides. Study sites such as Sparknotes.com and Cliffsnotes.com offer good examples of the form.
Avoid plagiarism. The summary should be in your own words, but if you do quote from the book, be sure to include a citation.
A book summary offers more plot synopsis and is more dispassionate than a book review; however, even in a book summary, you may be asked to include some of your personal responses to the text.