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 tête-bêche format. This is particularly true for the science fiction books, for which several bibliographic references have been written (see the References section). The format inspired a further series of sf doubles published by Tor Books between 1988 and 1991, the Tor Double Novels.
Because the tête-bêche format is part of the attraction for collectors, titles published between 1974 and 1978, which contained two titles by one or two authors but which are not tête-bêche, are not regarded by some collectors as true Ace Doubles. The distinction is up to each collector; the books are included in the list given below, with the difference in format noted.
The list given here includes an indication of the genre of the works, in italics after the serial number. Abbreviations used are "SF" for science fiction titles; "MY" for mystery titles, and "WE" for westerns. In addition, "NA" is used to mean "not applicable", when one or both of the books is not in one of these three genres; and "UN", when the genre of the books is not known. The list also 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.
The list is thought to be complete, but there may be minor omissions among the later lists.
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.
Read more about this topic: List Of Ace Double Novels