The crime fiction genre is a broad field which includes multiple sub-genres: old-style country house murder mysteries, police procedurals, courtroom dramas, psychological thrillers, location-based books such as Scandinavian or Scottish noir, and more. The emphasis nowadays is often on character and psychology rather than solving “whodunnit” puzzles, and there is an increasing overlap with general or literary fiction.
The classification of such books on Amazon is a great deal more complicated than the above descriptions might suggest. Many of the self-published authors I know are uncomfortable with internet marketing, or would rather spend their time on actual writing than on studying this aspect. But unless they know how to select categories and keywords wisely, their books will have little chance of being discovered by new readers. Having found it a challenge to use the system myself, I am writing this post to summarise my understanding of how it works. The following information will be too basic for experienced writers but may be useful for beginners. My examples relate to crime fiction but similar principles apply for any other genre. Plenty of more detailed advice can be found online.
Authors setting up their book descriptions on kdp (Amazon Kindle Direct Publishing) will be asked to select up to seven keywords. These can be either single terms or short phrases, and should be as specific to the content of the book as possible. There are certain rules regarding the choice of keywords, as explained below. Then they are presented with a list of categories corresponding to the BISAC (Book Industry Standards and Communications) system. They can select two categories from this list, and except for books that clearly belong to a specific sub-genre it is advisable to choose two different ones. For crime fiction, at least one of these would probably be “Crime” “Mystery and Detective” or “Thrillers”. Some books could also be put into other categories, for example “Family Life”. Again, is advisable to be as specific as possible by using the smaller subcategories as well as the main ones.
The chosen combination of keywords and BISAC categories will be used by Amazon to decide where to place the book in their system of “browse categories”, which number several thousand. A selection of these will be shown to potential readers who are searching the website for books of interest to them. For example, when I look on my computer for my favourite genre of “domestic noir”, a list of 20 other categories – 10 for books and 10 for Kindle – comes up on the left side of the screen.
Some categories have keyword requirements, for example a book will not be assigned to “Mystery, Thriller & Suspense/Mystery/Cozy/Culinary” unless one of the terms “food” “cook” or “bake” is included as a keyword. See this link for a full list of these regulations. Authors can email Amazon staff through Author Central to ask for their books to be placed in certain categories. There are minor variations between Amazon.com and Amazon.co.uk, and revisions are continually being made.
I also publish my ebooks on Smashwords.com which uses a simpler system. The categories “Mystery & Detective” and “Thriller & Suspense” each have five subdivisions. “Crime” can be found as a subcategory under “Themes and Motifs”.
The good news for self-published authors who find this topic daunting is that they can change their categories and keywords as often as they wish. It is therefore possible to experiment with what combinations are most successful, as measured by Amazon sales rankings – shown on Author Central pages, or at the bottom of the product description for each book – or better still by actual sales. But the field is so competitive that few unknown authors will achieve much success through optimal categorisation alone, and will need to use additional methods of marketing.