History of Penguin paperbacks

The possibly apocryphal story of the birth of Penguin paperback books begins in 1935 in a train station where the publishing house's founder, Allen Lane, couldn't find anything good to read in the shops. Supposedly, he flashed on the idea of making quality novels readily available for the same price of a pack of smokes. Smithsonian has a short history of "How the Paperback Novel Changed Popular Literature":

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The first ten Penguin titles, including The Mysterious Affair at Styles by Agatha Christie, A Farewell to Arms by Ernest Hemingway and The Unpleasantness at the Bellona Club by Dorothy Sayers, were wildly successful, and after just one year in existence, Penguin had sold over three million copies.

Penguin's graphic design played a large part in the company's success. Unlike other publishers, whose covers emphasized the title and author of the book, Penguin emphasized the brand. The covers contained simple, clean fonts, color-coding (orange for fiction, dark blue for biography) and that cute, recognizable bird. The look helped gain headlines. The Sunday Referee declared "the production is magnificent" and novelist J. B. Priestley raved about the "perfect marvels of beauty and cheapness." Other publishing houses followed Penguin's lead; one, Hutchinson, launched a line called Toucan Books.

With its quality fare and fine design, Penguin revolutionized paperback publishing, but these were not the first soft-cover books. The Venetian printer and publisher Aldus Manutius had tried unsuccessfully to publish some in the 16th century, and dime novels, or "penny dreadfuls" -lurid romances published in double columns and considered trashy by the respectable houses, were sold in Britain before the Penguins. Until Penguin, quality books, and books whose ink did not stain one's hands, were available only in hardcover.

"How the Paperback Novel Changed Popular Literature"