Ace books was started by AA Wyn in collaboration with Donald A Wolheim in 1952. In order to justify a 35¢ cover price, they devised the idea of publishing two complete novels back to back with a different cover for each side. Thus the Ace Double was born where each book was to include one reprint and one Paperback Original (PBO). This gave them a lot of latitude to introduce new authors on the coat-tails of more established writers. Their first book was D-1 Too Hot For Hell backed with The Grinning Gismo with cover art by Norman Saunders. Click on the cover on the left to see both sides. In 1954 single books began to appear with an S number to indicate a 25¢ cover price. After 1955, they specialized in the Science Fiction genre and published almost 80 Ace Science Fiction Doubles.
The most famous Ace Double is Junkie by William Burroughs written under the pseudonym "William Lee", the 'confessions of an unredeemed drug addict'. It was backed with Narcotics Agent to balance the Burroughs book with a moral message.