"What do you mean, 'real people'?"
"As opposed to people in books," Paola explained. "They're the only ones we ever really know well, or know truly." Again she gave him a moment to consider, then said, "Maybe that's because they're the only ones about whom we get reliable information." She glanced at him, then added, as she would to a class, just to see if they were following, "Narrators never lie."
Donna Leon, A Sea of Troubles
The narrator's truth is not the only truth in a novel. Some of the truth is what we find for ourselves, but that is a different kind of truth, which I will come back to in a little bit. For now let us consider what Paola says to her husband in the final paragraphs of this story.
She contrasts what we know about real people, even the people we are closest to, with what we know about the people in novels. In fiction, we know what people are thinking and exactly what they say. When the narrator tells us something happens, we know it happens in just that way. Sometimes, as in the final chapters in Leon's novel, what happens is a bit confusing, yet the narrator's version is all we have. It is the truth, the whole truth and nothing but the truth as far as these characters and this story is concerned.
History books and biographies are said to be nonfiction, yet we cannot know for certain that what their authors write is, in fact, the truth. Authors of nonfiction books can be mistaken or deliberately misleading, or they can be biased. Read different books about the same famous person or the same battle and you may read very different versions of the truth. In fiction there is but one truth, the truth the narrator tells.
Tan went on to say that fiction is about finding "a particle of truth," not necessarily the whole truth. And that particle may be different from one reader to the next, and no reader may find quite the same particle found there by the author.