I just finished a book that reads like a memoir although it is labeled fiction. This got me thinking about the difference between the two.
I think of Of Human Bondage, Somerset Maugham's classic coming-of-age story. Although Maugham admitted that this was basically his own story, through which he exorcised his demons from childhood, it comes across as fiction. Why?
When we write a story, all of the characters are invented by the author. Even when authors use people from their own lives as characters, they choose the characteristics of those people needed to make the story work. If a writer is competent, no real person makes it into a story unchanged because fiction writing involves selection -- selection of details that fit with what the author wants to say. And by selecting some characteristics and ignoring others, we implicitly alter a personality.
If a story is narrated in the first person, the same principle applies in terms of creating character. The only thing that differs is that, since the point of view is the narrator's, only what the narrator sees and knows and believes gets recorded. The only way -- and the prime way -- that the reader gets to know how others see the narrator, or that the narrator has a false view of himself, is to create situations in which other people in the story reveal -- usually through dialogue --how they see the character.
In a memoir, though, the writer is completely fused with the narrator. The writer is trying to tell the truth of his or her experience. But this is going to look different from the way it looks when, in fact, the narrator and writer are two different people. For one thing, none of us knows ourselves very well, and none of us knows ourselves the way others see us -- and everyone we know sees us differently! But there is a more important difference: although the fiction writer creates a fictional interior world for the first-person narrator, this is not the same kind of interior world a real person experiences. A real person has an implicit understanding of the world that is never voiced in words, even to himself. Why not? Because he has never known anything else! Language is about contrasts, and the fictional narrator can be created and defined by his characteristics because the writer knows what the myriad other possibilities are. But the real person has been "me" as long as he/she can remember and the world has looked as it looks through those same pair of eyes for a long as can be remembered. The only time, then, that we, in real life, give voice to our interior sense of the world is when something dramatic happens in our lives which causes us to question our implicit assumptions.
So, this is what makes memoir so tricky. There is an assumption that the world looks to others the way it looks to us -- and, more importantly, the unconscious assumption that our way of viewing the world is shared with our readers. When this assumption is never overcome, we end up with a piece of writing in which the writer thinks he/she has revealed something deep or true but the reader comes away thinking, "What was that all about?" And a memoir billed as a novel will have this same characteristic, because it really doesn't matter if the characters' names are changed or if some events didn't happen as portrayed: if the writer is not able to create a persona separate from the way she knows herself on the inside, the work will not succeed.