Size doesn’t matter, but at 784 pages, “The Collected Stories of Diane Williams,” new this month, outweighs the collected short fiction of Saul Bellow, Grace Paley, Gabriel García Márquez and almost any other writer one can name.

That size doesn’t matter is central to Ms. Williams’s work. This new book includes more than 300 stories published over the last 29 years; their average length is about two and a half pages. Within the very narrow confines of a Diane Williams story, the author might toy with metafictional device or offer something that hints at a plot, she might create character or capture a scene, she might show or simply imply something sexual, something violent or something merely unpredictable.

Ms. Williams is 72. She lives in the sort of Manhattan apartment realtors describe as “well-appointed,” with copious sun and art on display everywhere. She speaks candidly about her work and its relationship to her own life. In person, as on the page, Ms. Williams is funny and frank, as well as elusive. Her stories might be short but that is sleight of hand; they demand focus. “I don’t like to have it all wrapped up,” she said. “Hardly anything that matters in life is that easy.”

“I’ve heard lots of criticism of what I’m doing,” she said. “I’ve been told these aren’t stories.” Ms. Williams speaks deliberately, with a calm that is not dispassion but certainty. She sometimes closes her eyes, presumably to formulate her thoughts, then opens them when she’s ready to speak. “It enrages me.”