There are many ways to categorize mystery novels. Amazon, for example, has categories for serial murderers and British detectives among many others. I have my own system and I thought I’d share it with you here, both as a Venn diagram and a table. I’ll explain more after the images.
All mystery novels have some things in common – there’s a mystery, for one thing – and they have characters which they develop to some extent or another. I find that the best mysteries have one overweening characteristic that sets them apart. I’ve listed 20 mystery series or individual books that illustrate these features. I’ve shown them as four main subgenres: Procedural, Setting, Humor, and Action. Here’s how I define those:
1. Procedural – often called Police Procedural even though it applies to private detectives and amateurs as well, these emphasize the detailed, professional way the main investigator goes about the task of solving the case. The intelligence and inside knowledge of the investigator is the key feature. Michael Connelly’s Harry Bosch is the quintessential example. Sherlock Holmes fits here, but actually has a large action element, too.
2. Setting – These feature the setting, especially the geographic locale, but also the time frame or even vehicle/structure like a cruise ship or palace. Historical mysteries fall in this category, although I haven’t featured any on my chart. All stories have a setting, but I’ve chosen books where it is the predominate attraction of the book or series. You may quibble over Nancy Drew, but I include those here because many of her books were set in interesting places like the Crocodile Island one. Of course, how interesting or exotic a locale is depends heavily on the reader’s education and life experience.
3. Humor – These are characterized by a light, witty tone, or a black humor. Cozy mysteries always fit here although they have other elements. However, many regular, i.e. non-cozy mysteries also share this characteristic. Snappy dialogue is a typical trait of these. The delightful No. 1. Ladies’ Detective Agency series falls equally into Humor and Setting.
4. Action – These are typified by gunfights, fistfights, car chases, animal attacks, explosions or crashes, or to a lesser extent, suspense, such as whether a character will escape or survive a dangerous situation or pursuer. Virtually all mysteries have at least a bit of this, but only some have it as the main stylistic element for a series. I don’t like the Spenser books, but I’ve used them as an example of this type since that’s pretty much all they are – kick-ass action thrillers more than mysteries. Some LEO characters like Bosch and Pickett have substantial action elements, but the over-the-top stuff usually is confined to the private side because of the illegality of much of it.
I’ve also broken the diagram into black boxes to show the type of main character, usually the lead investigator. I don’t think that trait matters much to a mystery, not as much as the above subgenre anyway, but some people consider it important. There is also usually a lot of overlap. Amateurs and private eyes almost always have someone in the law enforcement world as a resource so that they can obtain police reports or other inside information not generally available to the public. Amateur is rather self-explanatory but may include some rather sophisticated investigators such as reporters. Police and Law Enforcement Officers (LEO) includes FBI, forest rangers, etc. Private Eye/Pro includes non-governmental professional investigators like Sue Grafton’s insurance investigator Kinsey Millhone and defense lawyers like Connelly’s Mickey Haller character (not on the chart). Many private eye protagonists are former LEO or may transition from one class to another during a series (e.g. Cliff Knowles). Making the main character a non-LEO provides the author a lot more freedom of action for the main character, but poses other problems.
It’s impossible to list all possible distinguishing traits of a book. Other factors some consider important or interesting are first person/third person; single/multiple narrators; unreliable narrator; age of the investigator; nature of the crime; amount of gore or bad language. I hope what I’ve chosen here is of use to you in evaluating a book.