"Graphic Novel" is a format, not a genre. Graphic novels can be fiction, non-fiction, history, fantasy, or anything in-between.
Graphic novels are similar to comic books because they use sequential art to tell a story. Unlike comic books, graphic novels are generally stand-alone stories with more complex plots. Collections of short stories that have been previously published as individual comic books are also considered graphic novels.
Major Types of Graphic Novels
Like traditional novels there are endless ways to categorize different graphic novels. There are as many genres and sub-genres as in traditional fiction and non-fiction. The following are only a few of the most predominant categories.
Manga: The Japanese word for "comic" but in the US is used to describe Japanese style comics. Manga is read from top to bottom and right to left as this is the traditional Japanese reading pattern. Though technically Manga refers to Japanese comics, many think Manga refers to a style rather than the country of origin.
Superhero Story: Superhero graphic novels have taken the most popular form of comics and turned what were once brief episodic adventures into epic sagas. Superhero comics are dominated by a few mainstream publishers such as Marvel, DC, and Darkhorse.
Personal Narratives ("Perzines"): are autobiographical stories written from the author's personal experiences, opinions, and observations.
Non-fiction: are similar to perzines in that they are written from the author's personal experience, but the author is generally using their own experience to touch upon a greater social issue.
(Content from https://www.buffalolib.org/get-graphic/what-graphic-novel)