What are book categories on Amazon and other stores?

Categories are the virtual shelves of an online bookstore, such as "Mystery, Thriller & Suspense > Mystery > Cozy". Readers browse them, stores use them in recommendations, and each category has its own bestseller list. Choosing the right ones is one of the most important metadata decisions for a self-published book.

Most stores outside Amazon use BISAC subject codes for categories. Amazon KDP uses its own category tree: when you publish, you currently choose up to three categories per edition, separately for eBook and print. Rules on how many categories you can pick and how to change them have changed over the years, so check KDP's current guidance.

Specific beats broad. A book in "Fiction > General" competes with almost everything, while a well-chosen sub-category puts it in front of readers looking for exactly that kind of book — and makes it more realistic to reach that category's top 100. Look at where comparable books in your genre are listed, and pick categories whose readers would genuinely want your book.

Do not choose unrelated categories just because they look easier to rank in. Readers there are not looking for your book, so it will not sell, and stores may move or penalise listings with misleading categories.