A graphic novel is just a long story in comic form. A typical monthly comic is some 22 pages and story arcs are typically 5-6 issues but can be shorter or longer. That arc can be combined into a graphic novel, though it's usually called a trade paperback. The graphic novel itself is one story, much longer than 22 pages. They can be shorter at 60-ish pages or much longer at 200. Usually 80-100 is average.