I wish somebody would collect all the pieces that George Tuttle has written about the field of paperback originals. For me he's the best historian that subject has ever had. I was reminded of this when I stumbled on his take on the emergence of hardboiled. http://www.geocities.com/SoHo/Suite/3855/
Here's a sample from the piece:
Noir came truly alive with the advent of the first line of paperback originals, Gold Medal Books. The paperback original provided noir with its medium. It was not as inhibited when it came to sex, and was willing to tackle this darker, more cynical type of fiction. It is not surprising that James M. Cain was able to publish Sinful Woman (1948), Jealous Woman (1951), and The Root of His Evil (1952) as originals when he had failed to sell them to hardcover or magazine markets.
Though Gold Medal published some test runs in late 1949 and early 1950, the line didn't become fully operational until May 1950. Gold Medal's relationship with noir fiction developed slowly and didn't truly come into full force until Richard Carroll became editor in February 1951. Carroll had worked previously as a story editor in Hollywood. This is possibly why he was open to this dark brand of crime fiction.
Gold Medal was the leader in noir fiction, discovering writers like Charles Williams, Peter Rabe, Gil Brewer, Clifton Adams, John McPartland, Marvin Albert, and Vin Packer, publishing noted works by Harry Whittington, Day Keene, Lionel White, Wade Miller, Bruno Fischer, David Goodis, Benjamin Appel, Dan J. Marlowe, and eventually, Jim Thompson.
Gold Medal realized quickly that noir was profitable. House of Flesh (1950) by Bruno Fischer sold 1,800,212 copies; Hill Girl (1951) by Charles Williams sold 1,226,890; 13 French Street (1951) by Gil Brewer sold 1,200,365; and Cassidy's Girl (1951) by David Goodis sold 1,036,497. Soon, other paperback publishers like Lion, Dell, Ace, Popular Library, Beacon, Monarch, and Avon followed Gold Medal's lead. Lion Books, in particular, carved its own special niche by brining Jim Thompson to the forefront.