Almost every Tobias Wolff story has a strange, unexpected moment when everything changes. And I mean everything. Characters, conflict, setting, chronology - all of these are up for grabs. You might even think you have accidentally fallen into a different story, or placed your bookmark on the wrong page.

A Wolff tale might start out with a student running into her art professor on campus - but by the end the story has morphed into a meditation on the moral dilemmas of a soldier in the Middle East. Another Wolff offering might begin with the gripping account of a bank robbery, but strangely evolve into a recollection, from decades before, of boys arguing over the relative merits of Mickey Mantle and Willie Mays. Or a narrative might open with a father beating off a wild dog who has tried to attack his daughter, but end up with a murder in another part of the city involving completely different people.

Wolff pulled off this stunt most outrageously in his celebrated novel Old School. Here the main character, who dominates the first 90% of the book, steps into the background in the final pages and allows another protagonist take center stage. Normally, I would see this shift in perspective as a flaw, a sign of authorial impatience or inability to control the structure of his narrative. In the case of Michael Ondaatje's recent novel Divisadero, readers encountered precisely this - several unconvincing shifts in focus that suggested a story running away from its author. But Wolff always knows exactly what he is doing, and when his books impose an unexpected change of scenery, it is usually in order to make a sly comment on everything that has gone before.

One might even accuse Wolff of trying to subvert the essence of the short story - which is usually focused on a single conflict and its resolution. Of course, Wolff doesn't write like a subversive. On the surface his prose is smooth and controlled, avoiding ostentatious effects, and sensitive to the small nuances of the moment. He is especially good at "coming-of-age" stories, tales involving students or soldiers or other young adults adapting to the demands of growing up. Nothing avant garde here — at least not at first glance. But Wolff's steadfast refusal to accept the traditional arc and closure of short fiction is more than an authorial quirk. Rather, it represents a radical attempt to bring some of the open-endedness of real life into his prose.

This author is especially good at setting up two different conflicts in the same story, and leaving it up to the reader to draw the connecting points. Wolff can present us with the mid-life crisis of a doctor, but let us discover that the real impetus for his malaise arises from a failed romance during his high school years. Or we can mull over the conflict between an editor and a journalist over a botched death notice, only to discover that the real story is found in the mysterious subject of the obituary.

In short, the three unities - Aristotle's rules for structuring dramatic accounts by tightly controlling their action, place and time - are replaced by three discontinuities in Wolff's writing. Is this experimental fiction? Not on the surface. But sometimes the best experiments are the ones we least notice.