In 1931, the German publisher Albatross Books was the first to produce a mass-market paperback book, but the approaching WWII prevented further marketing. In 1935, the British publisher Penguin Books began the paperback revolution in the English language book-market. In 1939, the Pocket Books label appeared in the United States. Thereafter, the term “pocket book” was synonymous with English language paperbacks in North America.
During WWII, American publishers collaborated to produce 1180 pocket-sized Armed Services Editions of popular books that were distributed free of charge to 16 million service men and women .
Read a fascinating article by Louis Menand: The Birth of Pulp Fiction – The New Yorker.