Quirk is a kind of writing that is part short story, part expository writing, part nonfiction, part fiction, and part anything else you can think of… even poetry if you so desire. Some good examples of Quirk can be found in this collection.
Quirk, as a literary style, has few rules to follow, if any. Flash Fiction or any of the shorter fictions can be considered forms of Quirk, but none of them defines it.
Quirk can tell a story, or merely make a stab at a story. It can also shaggy-dog its way down the page, even changing directions or subjects. Ultimately, Quirk is fun to both read and write, finally setting itself apart as its own literary subgenre originated by writers such as James Thurber and O. Henry.
