What is a novella?
It's a prose fiction which is longer than a long story, but shorter than a short novel. If that seems baffling, you could think of something around 30—40,000 words in length. But in fact, it's not word count which is the crucial factor.

The essence of a novella is that it has a concentrated unity of purpose and design. That is, character, incident, theme, and language are all focussed on contributing to a single issue which will be of a serious nature and universal significance.

Currently Pleasure of My Company, The: A Novella By Steve Martin see related