The flap of a book is the part of the cover folded to appear on the inside front and back of a book. Book flaps contain information designed to help sell the book, as well as information about the book's author. A book flap also typically includes a photograph of the author. Book flaps, also called jacket copy, are either written in house by staff writers or by the author himself. According a Codex Group study, jacket copy can have a definite impact on book sales, especially for fiction, and the importance of jacket copy can't be underestimated.
Write a synopsis of the book. The synopsis should give an overview of the book without giving away any of the key elements. Write the synopsis using strong, clear language. One of the goals of writing effective flap copy is to sell the story to potential readers with a sample. Like a food sample, you want to make potential readers want to buy the package. The synopsis runs 100 to 200 words, so each word you write needs to count.
Work in a blurb or two, set off in parentheticals, that you can integrate into the synopsis smoothly. If there are accolades from respected sources, such as the New York Times, include those. This material is often included on the back or front cover of a book, as well as inside the book, but one or two well-selected quotes or blurbs can strengthen the jacket copy.
Include an author's biography at the end of the synopsis. This typically lands on the back flap and includes about 50 words. The biography should include a brief overview of who the author is, some of his better-known works, and a one- or two-sentence description of where he lives, relationship status and sometimes reference to an upcoming or current project.