Supernatural fiction or supernaturalist fiction is a genre of literary and media fiction exploiting or requiring as plot devices or themes some contradictions of the commonplace natural world and materialist assumptions about it. Supernatural fiction continues to be popular, but because it is not simple to define and is not popularly understood, it is not used as a marketing category by publishers, booksellers, libraries, etc. When marketed, supernatural fiction is often classed as mainstream fiction, or is subsumed by other subgenres.