In high school I had an English teacher (American Literature) who liked to talk about The Great American Novel. Something about its scope and, like, defining a thing. Or something.
I assume he had never really read Huckleberry Finn.
Anyway, whatever else a novel is, it is something like a sandwich.
A sandwich is something between pieces of bread. (Regional and cultural definition of "bread" may vary.)
A novel is something between a front cover and a back cover. At least. Well that's a place to start.
So the Great American Novel would be text between covers that says something about America and is all defining and reconstructs the paradigms and all radiant and glorious and stuff. Depending on whether you're an English (AmLit) major.
What if there's no back cover?
Well then, if it's a traditional book you call it an unfinished novel, I guess. Author deceased.
Thought experiment: Think of a trilogy of books. I'm thinking of C. S. Lewis' space trilogy, but you can pick your own. Say the first book stands on its own as a story. Say books one and two likewise. Is the story complete? Along comes book three. Now what? What if there was a book that was a series of books but that was complete in every book? No real "back cover"? Complete in every chapter? But what if it kept on going, kept on growing, kept on attaining something -- complete and not-complete at every unit. Is book two of Lewis' space trilogy an unfinished novel? In what sense is it unfinished?
And what if the book has no covers? No paper at all? What if it is electronic / digital / internet based?
I think the English majors might not want to aim so low as to write a Great American Novel. Maybe it would be greater to aspire to being part of a kind of cohesive Homestuck that just keeps going and going and going. You may say I'm a dreamer. Together some day we may be writing the Great American Celebrate the Ongoing Life Thing. Maybe we already are.