A book cover includes all the essential information required to identify the work, including a title, the author's name, the ISBN and barcode, the retail price, and the name of the publisher. In the case of a paper wrap-around jacket, it also incorporates the front and rear flaps and introductory information about the book and perhaps the author. The design of a cover is important because it is what potential buyers or reviewers first see, and hence may determine whether or not they pick up the book. The overall design should therefore be eye-catching, ideally standing out from a large group of similar books. However, this is difficult to achieve.
A cover is normally uploaded as a single PDF file which incorporates front and rear covers, the spine and, where appropriate, the front and rear flaps. The front and rear covers each have the basic height and width of the book, and the spine width is determined by the number of pages included. Publishers generally have a simple calculator to determine the spine width. Bear in mind that pages are added to books in small increments - typical 4 pages at a time. The number of pages required for the book contents may therefore need to be rounded up to a number divisible by 4. Where front and rear flaps are incorporated, these have the same height as the book but a width of perhaps three or four inches. Remove the dust cover from any book to make sure that a custom design is laid out in the correct manner - ie with the front cover on the right side of the spine and the rear cover on the left.
Some POD companies have a library of standard cover designs upon which the relevant title, author's name and other supporting information can be printed. Others will create a custom cover in accordance with requirements but this involves an artist's time and can be an expensive process. The final option is for the author to produce a complete cover design and upload the PDF to the POD company.