Until the 1930s, a published book was largely known as a hardback. Softcovers would occasionally appear, but they didn’t really get much attention until the 1930s. By the 1940s paperbacks were a huge industry, appearing not in book stores but in drug stores, candy stores, airports, groceries, etc.
Initially they were twenty-five cents or less. Then, due to a lull in sales in the late 1940s publishers inserted as much sex into the covers and content as they could.
In 1943 Dell came up with a novel idea. To their line of mysteries they added a map to the back cover, depicting the locations of the novel. It was a hit. Countless Mapbacks were published, extending to other genres.
Many of the early covers were airbrushed/painted by Gerald Gregg (1907-1985). Later covers were the work of Robert Stanley (1918-1996) and Bill George (1930-2017). As for the maps, much is not known, but Ruth Belew (1898-1973) may have drawn them all, but records can only confirm 150.
Mapbacks continued until 1952, producing a total of 577 numbers. While they lasted, they were interesting, unique and ultimately had a good decade-long run. This is what they looked like.