Genre fiction, also known as formula fiction or popular fiction, is a term used in the book-trade for fictional works written with the intent of fitting into a specific literary genre in order to appeal to readers and fans already familiar with that genre.

A literary genre is a category of literature. Genres may be determined by literary technique, tone, content, or length. They generally move from more abstract, encompassing classes, which are then further sub-divided into more concrete distinctions. The distinctions between genres and categories are flexible and loosely defined, and even the rules designating genres change over time and are fairly unstable.