Complex sentence: These characters have long been a staple of detective mystery crime fiction, particularly in detective novels and short stories, many of which were set in Britain and written during the "Golden Age of Detective Fiction" (1920s-1930s).
Split into simpler sentences: These characters have long been a staple of detective mystery crime fiction, particularly in detective novels and short stories. Much of early detective fiction was written during the "Golden Age of Detective Fiction" (1920s-1930s).