first book published by Ace was a pair of mysteries bound tête-bêche: Keith Vining's Too Hot for Hell, backed with Samuel W. Taylor's The Grinning Gismo, priced at 35 cents, with serial number D-01. A tête-bêche book has the two titles bound upside-down with respect to each other, so that there are two front covers and the two texts meet in the middle (sometimes with advertising pages in between). This format is generally regarded as an innovation of Ace's; it was not, but Ace published hundreds of titles bound this way over the next twenty-one years. Books by established authors were often bound with those by lesser-known writers, on the premise that this would help new writers gain readers. The main drawback of the "Ace Double" format was that the two books had to fit a fixed page length (usually totalling between 256 and 320 low-height pages); thus one or both novels might be cut or revised to fit. Despite the tag "Complete and Unabridged" on the cover, books so labeled were sometimes still abridged. Some important titles in the early D-series novels are D-15, which features William S. Burroughs's first novel, Junkie (written under the pseudonym "William Lee"), and many novels by Philip K. Dick, Robert Bloch, Harlan Ellison, Harry Whittington, and Louis L'Amour, including those written under his pseudonym "Jim Mayo". The last Ace Double in the first series was John T. Phillifent's Life with Lancelot, backed with William Barton's Hunting on Kunderer, issued August 1973 (serial #48245). Although Ace resumed using the "Ace Double" name in 1974, the books were arranged conventionally rather than tête-bêche. 1953–1963: Genre specialization Ace's second title was a western (also tête-bêche): William Colt MacDonald's Bad Man's Return, bound with J. Edward Leithead's Bloody Hoofs. Mysteries and westerns alternated regularly for the first thirty titles, with a few books not in either genre, such as P. G. Wodehouse's Quick Service, bound with his The Code of the Woosters. In 1953, A.E. van Vogt's The World of Null-A, bound with his The Universe Maker, appeared; this was Ace's first foray into science fiction. (Earlier in 1953, Ace had released Theodore S. Drachman's Cry Plague!, with a plot that could be regarded as science fiction, but the book it was bound with—Leslie Edgley's The Judas Goat—is a mystery.) Another science fiction double followed later in 1953, and science fiction rapidly established itself, alongside westerns and