Novellas are a form of short fiction, typically between 17, 500 and 40, 000 words in length. They are longer than short stories but shorter than novels, and often focus on a single plot or theme. Novellas can be stand-alone works or part of a larger series. They are a popular form of literature, with many classic works such as Heart of Darkness by Joseph Conrad and The Metamorphosis by Franz Kafka being novellas.