Before we get into the nitty gritty of the Before You Write a Mystery Series, let's consider the types of mysteries so you can get a feel for what you want to write.
There are four traditional types of mysteries. They are:
Cozy Mystery: The traditional cozy mystery is usually about an amateur sleuth who has no intention of becoming a detective. The setting includes a small town and a limited sphere of people. Often some of the characters recur in the books within a series. In many cases, the sleuth is a woman, middle age or older, who has some other responsible job, such as librarian, etc. The murder in a cozy is usually quick with little gore to upset the reader. The story revolves around the interesting untangling of facts that lead to the discovery of the murderer. Sometimes, cozy mysteries are not about murder, but usually they are. Examples of cozy mysteries are: Agatha Cristie books, books about Miss Marple, Lillian Jackson Braun's The Cat who... series, and the TV series Murder She Wrote.
Police Procedural: The simple explanation of this type of mystery is that it is a novel that deals realistically with police work. Accuracy is important in police procedurals. You can not make up procedures for them to follow in investigating a crime. The readers know what is authentic. In many cases, the characters will be investigating a primary case but will be shown attending to other current cases as well. Also, it is usually written from the point of view of the policeman or detective investigating the crime. Sherlock Holmes is an example of this. On TV, Law and Order is a police procedural.
Hardboiled Detective: A street-wise, hardened, private investigator/detective is at the center of a hard-boiled, detective novel. Examples of this type of fiction are numerous from authors such as Mickey Spillane, Robert B Parker, Sue Grafton, John D. McDonald, and Sara Paretsky. These wonderful characters lend themselves to serialization.
Mystery: General mystery fiction is not as concentrated only on procedures or on solving the crime. In addition, the emphasis is on a story, about the characters and about how they are related to the story and the crime.
Thrillers: Off-shoots of the mystery genre is the category of thriller. Usually there is an element of mystery to thrillers that keep pages turning. There are many categories under the thriller column, such as action thrillers, conspiracy thrillers, disaster thrillers, legal thriller, political thriller, etc.
Suspense: Suspense fiction is a broader mystery category than thriller. It can be mildly suspenseful or a nail-biter. There are many specific cross-genre novels that fall into the suspense category, such as romantic suspense, western suspense, etc.
Think through all the types of mystery books in your personal library. Which ones do you reach for more often? You might take guidance from these in preparing to write your own novel. Put some time into narrowing down your favorite type and this may help prepare you to write your novel.
What's your favorite and why?