I know this sounds like a stupid question. A novel is fiction by defintion - end of story. But, what if it is a fictional story based on truth? Is it automatically historical fiction? (To me, historical fiction only means it is based on soemthing famous - like a fictionalized story of Geroge Washington and the Red Coats flying to the moon, lets say.)
But, if a “novel” were promoted as “based on a true story”, is it still a novel? And if so, does it default into being “historical fiction”? …If not, then what is it?
Norman Mailer, Truman Capote et al. would agree, having written several novels (Executioner’s Song, In Cold Blood) based strictly on historical data. Whether they’re really novels, of course, is open to conjecture.
A novel, even if it’s based on a true story, is assumed to be a made-up story and thus is differentiated from an account that presumes to be the truth. In addition, a novel uses different techniques (e.g., quoting long conversations) that are not usually done in nonfiction. Mailer and Capote both uses the novelistic techniques to tell a true story and called it a “nonfiction novel.”
The umbrella term for a story is narrative–narratives can be fiction or non-fiction. A novel is a fictional narrative. The sort of thing you are talking about can be called a narrative, or, if you want to be more specific, a “novel-length narrative”.