An Illustration printed on a paperback cover. This decorative practice began in the early 1850s, with the publication of Letters Left at the Pastry-Cook's by J.S. Mayhew, and was the precursor of the next trend in publishing-yellowbacks. The sensational pictorial paper cover novels of the later 19th and 20th centuries are famous for their lurid, colorful covers. Also known as illustrated wraps.