Following the 1987 initial release of Games Workshop’s Warhammer 40,000 wargame the company began publishing background literature that expands previous material, adds new material, and describes the universe, its characters, and its events in detail. Since 1997 the bulk of background literature has been published by the affiliated imprint Black Library.
The increasing number of fiction works by an expanding list of authors is published in several formats and media, including audio, digital and print. Most of the works, which include full-length novels, novellas, short stories, graphic novels, and audio dramas, are parts of named book series. — Wikipedia