Back when people had to leave the house if they wanted to buy something, the biggest problem in the book business was bookstores. There were not enough of them. Bookstores were clustered in big cities, and many were really gift shops with a few select volumes for sale. Publishers sold a lot of their product by mail order and through book clubs, distribution systems that provide pretty much the opposite of what most people consider a fun shopping experience—browsing and impulse buying.

Book publishers back then didn’t always have much interest in books as such. They were experts at merchandising. They manufactured a certain number of titles every year, advertised them, sold as many copies as possible, and then did it all over the next year. Sometimes a book would be reprinted and sold again. Print runs were modest and so, generally, were profits.

Then, one day, there was a revolution. On June 19, 1939, a man named Robert de Graff launched Pocket Books. It was the first American mass-market-paperback line, and it transformed the industry. Whether it also transformed the country is the tantalizing question that Paula Rabinowitz asks in her lively book “American Pulp: How Paperbacks Brought Modernism to Main Street” (Princeton). She builds on a lot of recent scholarship on the way that twentieth-century literature has been shaped by the businesses that make and sell books—work by pioneers in the field, like Janice Radway and Lawrence Rainey, and, more recently, scholars like Evan Brier, Gregory Barnhisel, and Loren Glass. Paperbacks, even paperbacks that were just reprints of classic texts, turn out to have a key part in the story of modern writing.

Neither the theory nor the practice of mass-market-paperback publishing was original with de Graff. Credit is usually given to an Englishman, Allen Lane, who was the founder of Penguin Books. According to company legend, as Kenneth Davis explains in his indispensable history of the paperback book, “Two-Bit Culture,” Lane had his eureka moment while standing in a railway station in Devon, where he had been spending the weekend with the mystery writer Agatha Christie and her husband. He couldn’t find anything worthwhile to buy to read on the train back to London. And so, in the summer of 1935, he launched Penguin Books, with ten titles, including “The Murder on the Links,” by Agatha Christie. The books sold well right from the start. It helped that Penguin had the whole British Commonwealth, a big chunk of the globe in 1935, as its market.

Paper book covers are almost as old as print. They date back to the sixteenth century, and paperbacking has been the ordinary mode of book production in France, for instance, for centuries. The first edition of James Joyce’s “Ulysses,” published in Paris in 1922, is a paperback. In the United States, paperback publishing was tried on a major scale at least twice during the nineteenth century: first, in the eighteen-forties, with an enterprise called the American Library of Useful Knowledge, and after the Civil War, when, unfettered by international copyright agreements, American publishers brought out cheap editions of popular European novels.

The key to Lane’s and de Graff’s innovation was not the format. It was the method of distribution. More than a hundred and eighty million books were printed in the United States in 1939, the year de Graff introduced Pocket Books, but there were only twenty-eight hundred bookstores to sell them in. There were, however, more than seven thousand newsstands, eighteen thousand cigar stores, fifty-eight thousand drugstores, and sixty-two thousand lunch counters—not to mention train and bus stations. De Graff saw that there was no reason you couldn’t sell books in those places as easily as in a bookstore.

The mass-market paperback was therefore designed to be displayed in wire racks that could be conveniently placed in virtually any retail space. People who didn’t have a local bookstore, and even people who would never have ventured into a bookstore, could now browse the racks while filling a prescription or waiting for a train and buy a book on impulse.

Getting the books into those venues did not require reinventing the wheel. Instead of relying on book wholesalers—“jobbers”—who distributed to bookstores, de Graff worked through magazine distributors. They handled paperbacks the same way they handled magazines: every so often, they emptied the racks and installed a fresh supply.

Pocket books were priced to sell for twenty-five cents. De Graff is supposed to have come up with that figure after paying a quarter at a toll booth. No one, he concluded, misses a quarter. Penguins sold for sixpence: Lane believed that his books should not cost more than a pack of cigarettes. This meant that people could spot a book they had always meant to read, or a book with an enticing cover, and pay for it with spare change.

De Graff road-tested his idea in New York City, selling Pocket books in subway newsstands and similar outlets. He knew he had a winner when a hundred and ten books were sold in a day and a half at a single cigar stand. By mid-August, after eight weeks and with distribution expanded to the Northeast corridor, de Graff had sold three hundred and twenty-five thousand books. He had discovered a market. The same month, Penguin opened an American office. Others rushed to compete: Avon started up in 1941, Popular Library in 1942, Dell in 1943, Bantam in 1945, and, after the war ended, half a dozen more, including, in 1948, New American Library (N.A.L.), which published the Signet (fiction) and Mentor (nonfiction) imprints. The paperback era had begun.

Paperbacks vastly expanded the book universe. The industry had got a taste of the possibilities during the war. Encouraged by the success of Pocket and Penguin, publishers collaborated to produce Armed Services Editions of popular titles—double-columned paperbound books, trimmed to a size that slipped easily into the pocket of a uniform, and made to be thrown away after use. The books were distributed free of charge to the sixteen million men and women who served during the war. (Publishers also offered their own books for sale to the troops.) According to Rabinowitz, eleven hundred and eighty titles were published in Armed Services Editions, and an astonishing 123,535,305 books were distributed, at a cost to the government of just over six cents a copy.

Servicemen and women stationed overseas were a captive audience, but many came home having acquired a habit of reading for pleasure and a comfort with disposable paperbacks. In 1947, two years after the war ended, some ninety-five million paperback books were sold in the United States. Paperbacks changed the book business in the same way that 45-r.p.m. vinyl records (“singles”), introduced in 1949, and transistor radios, which went on sale in 1954, changed the music industry, the same way television changed vaudeville, and the same way the Internet changed the news business. They got the product cheaply to millions.

Paperbacks also transformed the culture of reading. De Graff was a high-school dropout (as was Lane, who left school when he was sixteen), and he seems not to have been much of a reader. He had no apparent investment in the notion of books as uplifting. “These new Pocket Books are designed to fit both the tempo of our times and the needs of New Yorkers,” he announced in a full-page ad in the Times the day his new line went on sale. (The copy was written for him by someone from an advertising agency.) “They’re as handy as a pencil, as modern and convenient as a portable radio—and as good looking.” Books were not like, say, classical music, a sophisticated pleasure for a coterie audience. Books were like ice cream; they were for everyone. Human beings like stories. In the years before television, mass-market paperbacks met this basic need.