Ace Books published 250 western Ace doubles between 1952 and 1973 in dos-à-dos format. Genres and collectability Ace published science fiction, mysteries, and westerns, as well as books not in any of these genres. Collectors of these genres have found the Ace doubles an attractive set of books to collect, because of the unusual appearance of the dos-à-dos format. The list given here gives a date of publication; in all cases this refers to the date of publication by Ace, and not the date of original publication of the novels. For more information about the history of these titles, see Ace Books, which includes a discussion of the serial numbering conventions used and an explanation of the letter-code system. D Series D-002 WE William Colt MacDonald Bad Man's Return / J. Edward Leithead Bloody Hoofs (1952) D-004 WE Lewis B. Patten Massacre at White River / Walker A. Tompkins Rimrock Rider (1952) D-006 WE William E. Vance The Branded Lawman / Nelson C. Nye Plunder Valley (1952) D-008 WE Allan K. Echols Terror Rides the Range / Tom West Gunsmoke Gold (1953) D-010 WE Leslie Scott The Brazos Firebrand / Gordon Young Hell on Hoofs (1953) D-012 WE Dudley Dean Mcgaughy (as Dean Owen) The Man From Boot Hill / Dan J. Stevens Wild Horse Range (1953) D-014 WE Paul Evan Lehman Vultures On Horseback / George Kilrain Maverick With A Star (1953) D-018 WE J. Edward Leithead The Lead-Slingers / Samuel Peeples (as Brad Ward) The Hanging Hills (1953) D-020 WE Roy Manning The Desperado Code / Allan K. Echols Double-Cross Brand D-022 WE Bliss Lomax Maverick Of The Plains / Leslie Scott Badlands Masquerader (1953) D-024 WE Tom West Vulture Valley / John Callahan The Sidewinders (1953) D-028 WE Paul Evans Gunsmoke Kingdom / William E. Vance Avenger From Nowhere (1953) D-030 WE George Kilrain South To Santa Fe / Samuel Peeples (as Brad Ward) Johnny Sundance (1953) D-034 WE Ken Murray Hellion's Hole / Ken Murray Feud In Piney Flats (1953) D-038 WE Bliss Lomax Outlaw River / Louis L'amour (as Jim Mayo) Showdown At Yellow Butte D-039 WE Frank Gruber Quantrell's Raiders / Frank Gruber Rebel Road (1953) D-042 WE Walker A. Tompkins One Against The Bullet Horde / Charles M. Martin Law For Tombstone (1954) D-046 WE Chuck Martin Law From Back Beyond / Roy Manning Vengeance Valley (1954) D-048 WE Louis L'Amour (as Jim