Blade Runner (a movie) is a novella written by famous Beat Generation writer William S. Burroughs that was based on the original novel by Nourse. Both Nourse's novel and Burroughs' novella tell the story of a futuristic yet apocalyptic world in which Blade Runners are smugglers of medical equipment such as scalpels.
Despite the brilliance of Philip K. Dick's Do Androids Dream of Electric Sheep? the title of his celebrated novel is arguably too ambiguous for a major film. In the novel, Deckard is referred to plainly as a police officer and a bounty hunter, not a Blade Runner as he's known in the film. The words 'Blade Runner' and 'Replicant' don't appear in the novel at all, making them excellent additions by Scott and screenwriters Hampton Fancher and David Peoples