A paperback was a type of book.
Known paperbacks included Doctor Who in an Exciting Adventure with the Daleks, (PROSE: Bafflement and Devotion) Cold Comfort Farm, (PROSE: The Party in Room Four) and Tom's "Wildthyme" novels. (AUDIO: Wildthyme at Large)
There were hundreds of books in Paul Magrs and Jeremy's possession; many were kept in their bedroom (the ones kept nearest to the floor were often Fester Cat's targets for scratching) and in their Beach House. (PROSE: The Story of Fester Cat)
In the lower floor of the Celestial Omnibus, there was a bookcase filled with paperbacks. (PROSE: Enter Wildthyme)