what is the genre of the latter work?
UNANSWERABLE
what does 'ace books' mean? A publisher of science fiction and fantasy books who founded it? Aaron A. Wyn name some of the famous books they have published? William Colt MacDonald's "Bad Man's Return", P. G. Wodehouse's "Quick Service
wiki:6445153
Ace Books [SEP] 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 SF, but the book it was bound with—Leslie Edgley's "The Judas Goat"—was not SF.) Another SF double followed later in 1953, and SF rapidly established itself, alongside westerns and mysteries, as an important part of Ace's business.