The mystery genre has a deep subgenre which defines the degree of adult language, the amount of gore, the type of sleuth and even the level of investigation, among other things. Understanding your subgenre will help you market the story to the write audience and sell it to the right publisher.
Amateur Sleuth: the murder is solved by an ordinary person, as opposed to a professional detective or police office.
Classic Whodunit: a murder is solved by a private eye, generally written in first person from the detective’s point of view.
Comic: a murder investigation is played for laughs, often featuring a bumbling detective who is grossly unskilled, but manages to solve the crime despite himself. Inspector Gadget and Inspector Clouseau come to mind.
Cozy: a mystery in which sex and violence are downplayed or treated humorously, and the murder takes place in a small, socially intimate community where an outside, often eccentric detective investigates.
Dark Thriller: a mystery that ventures slightly into the horror genre, with intensified suspense and violence.
Forensic: a murder solved by a crime lab team who analyse, identify, and interpret the physical evidence. They reconstruct events to prove a crime was committed, and to connect a suspect to that crime.
Historical: a mystery that takes place in a distinct, recognizable era of history, with a great deal of emphasis on describing the details of the setting.
Legal: a mystery that takes place largely in the court room or within the justice system, and often features a defense attorney believing his client is innocent and trying to prove it.
Locked Room: a murder that appears to have been committed under impossible circumstances — such as a room with a locked door and windows and no visible sign of entry.
Police Procedural: a murder investigated from the perspective of police detective, with a great deal of emphasis on detailed, real-life police procedures.
Hard Boiled: A murder investigated by a tough-guy, private investigator for hire, who generally operates outside the long arm of the law and plays by his own rules. These are generally told from the first person Private Eye’s Point of View.
Noir: Generally a dark, disturbing narrative told from the point of view of the victim, a suspect or the murderer.
Psychological Suspense: mysteries focused the Why-dunit, not only delving into what motivated the murderer to commit the crime, but often why the sleuth is driven to investigate, and even why the suspects are driven to lie, cheat and mislead the poor sleuth
Romantic Suspense: a murder mystery which devotes an equal amount of the plot to the basic romance formula (boy meets girl, boy loses girl, boy gets girl back).