Adult literature is literature not considered suitable for children. Generally this means literature with an erotic or sexual theme, although in some cases it may include literature with violent subject matter, or other categories.
Usually the term is not used to include classical literature or "great books", even when the subjects include some degree of explicit eroticism. However, this exception is less marked for written literature than for visual art. "Adult literature" includes pornography, but is not limited to pornography nor even to erotica. Strictly speaking, this is not a legal term, but it is most often used in connection with legal or quasi-legal forms of restriction or censorship, intended to keep such literature away from children.