It is hard to define the novella. It is variously described as a long short story, or a short novel. It can be measured as having as few as twenty thousand words, or as long as fifty thousand. Readers will recognize the classic form in Dickens’ A Christmas Carol, James’ The Turn of the Screw, Kate Chopin’s The Awakening. There are many, many others. One of the things that attracts readers to them is they can generally be read in one long sitting.
What is not so often recognized is that the novella is quite often the form that fiction for young people takes. It has a wonderful structure, which calls for plot conciseness, sharp writing, and emotional impact. It also calls for writing tightness and sharply defined characters. Some of my own books, The Barn, The Christmas Rat, The Fighting Ground, and Poppy, take this form, and are (I think anyway) my best books.
The computer, I think, makes the work of writing long novels easier. Perhaps too much so. Anyone who can recall typing a long manuscript will know whereof I speak. Typing led to self-editing—if only to reduce the physical demands. There is the old saying, “Less is more.” Consider the novella and experience that for yourself.