A brief fictional narrative that can be read in one sitting?

How brief? Some people do 4 hours in one sitting. There's a semi-famous one called "A Day in the Life of Ivan Desenovich" it's a little over 100 small. It took me an hour and a half to read.

Most likely, what is meant here is called a short shory. Often there are no more than 20 pages, though length isn't what distinguishes this type of literature. Generally, there is only one main plot and just a handful of characters. A novel has multiple plots woven together and can have many characters.