what are the characteristics of the first one?
is a genre of speculative fiction with concepts such as advanced science and technology, space exploration, time travel and extraterrestrial life.
Science fiction
 is a genre of speculative fiction that typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel universes, and extraterrestrial life.
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 what is the genre of the latter work? UNANSWERABLE when was it published? 4 October 1940 what sort of struggles did they face financially? After the death of Wyn, the company grew financially overextended, failing to pay its authors reliably. do they publish books of different genres? Yes, of science fiction, mysteries and westerns combined,  lurid juvenile delinquent novels
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Science fiction [SEP] Introduction
Science fiction (sometimes shortened to sci-fi or SF) is a genre of speculative fiction that typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel universes, and extraterrestrial life. It has been called the "literature of ideas", and often explores the potential consequences of scientific, social, and technological innovations. Science fiction, whose roots go back to ancient times, is related to fantasy, horror, and superhero fiction, and contains many subgenres. Its exact definition has long been disputed among authors, critics, scholars, and readers. Science fiction literature, film, television, and other media have become popular and influential over much of the world.