Although I am primarily a chronic truth-seeker, which puts me in the "journalist" box, I have never been able to confine myself to the strict How Why What Where When of the dispassionate newspaper or broadcast journalist. The term Narrative Nonfiction is relatively new, but I have been practicing it since long before I knew it had an official name.
It doesn't matter which of the three subgenres you choose to follow, they all have one rigid rule that binds them together: your story must tell the truth and deal with facts. That is, it must be a factual account about a real person or a real event. Otherwise, while your embellishment might make it a better story, it becomes no longer nonfiction, you see.
A regular-flavor journalist collects a list of facts and then sits down and rewrites that list of facts into prose form, of a terse sort, for a newspaper to print or for a TV news reader to read. That's not me. I did that for a radio station once for about 3 years and then went out and committed suicide. I don't recommend it. (Ok, let me come clean: I wasn't writing facts. I was writing commercials. Hence the taking of my own life.)
Narrative Nonfiction, in all three varieties, is different in that it tells a real story using literary rules and customs; it does more than just string a list of facts together. I like to tell stories. I don't particularly like to make up those stories in my head. I like to research facts like a detective and then spin the yarn about the people or events. I don't make up extra things that didn't happen and I don't speculate on what people might have said. But it is a story, nevertheless, and it READS like a story.
A writer of narrative nonfiction does a hell of a lot more research than a newspaper reporter would do. Months of research, just like a good novelist does if he wants to make his fiction fact-based (like Gore Vidal's painstakingly researched novel "Lincoln," for example.) First, the narrative nonfiction author reads everything he can find about the person or event. He reads and reads and reads until he can close his eyes and tell the story from memory. If possible, he visits the person or site and does interviews. And he always brings his camera. Because of this, he ends up with a heck of a lot of interesting tidbits that the slam-bam hack journalist isn't going to be aware of and thus can't write about.
Top-notch narrative nonfiction writers make big money, but they obviously can't crank out a book every 2 or 3 months. A book every 2 or 3 years is probably more like it, and then only if they are constantly on the move and on the write. I equate narrative nonfiction writers with independent documentary film makers. Except that I have to paint the movies scenes with words. A poor-man's filmmaker. But I always carry my still camera because I know very well that one picture is worth a thousand words, many times. Maybe my pictures don't move, but it is a lot cheaper than a camera crew.
I have my favorite Narrative Nonfiction writers, of course, and I try to learn from them. Some are alive, some are dead. That's one of the good things about being an author — your stuff can still teach after you're dead. Pulitzer Prize-winner David McCullough is a favorite. (Amongst the living, thankfully.) His recent massively documented "John Adams" is more than just a good biography; it is a treasure for generations to come. That's a story about a person. His first blockbuster (if nonfiction can ever be called that) was written back in the sixties about a disaster that happened in 1889, "The Johnstown Flood," is a story about an event.
Who else? Studs Terkel. Studs isn't with us anymore, passed away in 2008, aged 96. Studs was much more than a writer, of course. Some of Studs' books are interviews which tell the story all by themselves. Do yourself a favor and read "Working" sometime. Or "Hard Times." The latter an oral history of the Great Depression; the former interviews with the common man (and woman) about their jobs and their aspirations.
That's all I have to say about that, I guess. The point? Good storytellers don't HAVE to be novelists.