I'm shooting for "Shamus Who Has Seen It All" level:
The Whodunit: The classic crime puzzle. The story generally revolves around determine who committed the crime, and potentially apprehending them. Some Whodunits, called "fair play mysteries", will include all of the clues available in the text so that a careful reader can solve the crime on his or her own.
Locked Room Mystery: Like the Whodunit, there is a puzzle (crime) to solve. However in this instance, the crime has taken place under impossible circumstances, such as in a locked room or on an island with no way to exit or enter.
Cozy: The nice person's mystery. Often the crime, particularly if it's violent, occurs off scene. Sex and language are on the cleaner side. Humor is a common feature of the cozy.
Hard-Boiled/Noir: Often cynical, bleak or realistic, hard-boiled and noir stories often focus more on the characters involved instead of the crime. Violence and sex are not downplayed.
The Inverted Detective Story: In this style of story, the person perpetrating the crime is known up front. The point of the story is to see how (or if) the detective goes about solving the crime and how the perpetrator reacts to the investigation.
The Historical Whodunnit: Simply put, this is a mystery set in a historical setting. Often the mystery has some historical significance and features detection methods that are appropriate for that era.
The Police Procedural: Instead of featuring a independent detective, the police are investigating the crime in these stories. They often focus on the actual methods that police officers use to solve crimes.
The Professional Thriller: This kind of mystery involves a professional who is not involved directly in law enforcement, such a lawyer or doctor, who nonetheless finds themselves investigating a crime.
The Spy Novel: Related to the other professional mysteries, spy novels focus on intelligence operatives as they work to prevent or avenge some criminal plot. Spy novels can feature either in fantastic or realistic settings.
Caper Stories: While other crime and mystery stories look at the aftermath of crimes, caper stories feature criminals as the lead characters. The story usually details the planning and commission of a crime.
The Psychological Suspense: In these stories, the detective story takes on a psychological component.
Spoofs and Parodies: Spoofs and parodies make light of crime fiction, often with the goal of commenting on the conventions of the genre. Many feature famous characters, e.g. Sherlock Holmes, James Bond, Philip Marlowe, or pastiches of those characters.
The Merely Mystery Reading Challenge will last the entire year (January 1, 2012 to December 31, 2012), giving participants a chance to read at their own pace. In addition, to make things easy, participants can complete one of two levels. One is for those of you who want a more relaxed challenge while the other is for those more serious about exploring the various sub-genres:
Down on Her/His Luck Gumshoe - Read two or more books falling into any of the above sub-genres. Each book can be from the same sub-genre or can be varied among the different sub-genres. You pick the combination and the number of books.
Shamus Who Has Seen It All - Read at least one book from each of the sub-genres for a total of 12 books. If you are feeling ambitious, read more than one book from each sub-genre.
