I have always understood "novel" to refer specifically to a long, written, fictional tale. Novelists are distinct from nonfiction writers.
At my library, there is a section marked for "graphic novels" that contains both fiction and nonfiction. Wikipedia claims repeatedly that "graphic novel" just has a looser definition than "novel" and is not necessarily restricted to works of fiction but I notice that these repeated claims are not supported by citation, whereas the version of the definition that's explicitly restricted to fiction is cited as coming from Merriam-Webster.
I understand that there are different camps with regard to what makes a definition "correct" or not. What I'm concerned with here is clear communication. An increasing number of biographies, autobiographies and historical accounts seem to be using this format; if I refer to them as "graphic novels," am I giving the false impression that they are fictions? Is there a contemporary term for long-form, graphic nonfiction works that's less ambiguous?