The Murder At The Vicarage , the first Miss Marple story, was published in 1930. Much more than any other of Agatha ‘s books (nearly all of which belong to it) this story belongs to the Cozy Mystery Genre. For the uninitiated, I have put down below the Wikipedia definition of a Cozy Mystery:
Cozy mysteries, also referred to as “cozies”, are a subgenre of crime fiction in which sex and violence occur off stage, the detective is an amateur sleuth, and the crime and detection take place in a small, socially intimate community. Cozies thus stand in contrast to hardboiled fiction, which features violence and sexuality more explicitly and centrally to the plot. The term “cozy” was first coined in the late 20th century when various writers produced work in an attempt to re-create the Golden Age of Detective Fiction.