Narrative nonfiction
Narrative nonfiction is NOT:
A "novel" is a work of the imagination, a work of fiction. And the word "based" indicates that the author doesn't stick to the facts.
So what is "narrative nonfiction"?
Carol Baxter writes history so this can be defined as:
Carol sticks to the facts in her books.
What makes them "gripping" — that is, what led The Times (London) to write of The Peculiar Case of the Electric Constable that it is "as lively and readable as a crime novel" — is the result of her literary style.
Narrative nonfiction writers appropriate the literary tools used by fiction writers to craft engaging nonfiction. It's about the choice of words and how those words are brought together to craft phrases, sentences and chapters. It's about the style, tone and voice used by the author. It's about the literary structure chosen to communicate the story.
Carol does not make up dialogue. She does not make up characters or scenes or descriptions. If she wants to know what the weather was like at the time of an event, she has to research it.
Narrative nonfiction is not "a novel based on a true story". Instead, it communicates the facts using an engaging literary style.
Creative nonfiction
Technically, "narrative nonfiction" and "creative nonfiction" are the same genre — according to the man who crafted the term "creative nonfiction".
However, today, many authors (and even writing teachers) think that the word "creative" gives them permission to do whatever they want with a true story. They can make up dialogue. They can "imagine" scenes. They can describe a room without having any evidence to support their description.
These days, many works of creative nonfiction really are little more than "a novel based on a true story".
What does Carol Baxter teach?
Carol doesn't teach her students how to write "creative nonfiction". She teaches them the craft of writing narrative nonfiction — that is, how to communicate the facts in an engaging way.