The Trick of It - Michael Frayn

He knows everything about her before they meet; more about her nine novels that she does herself. He has devoted his life to studying and teaching them, even though he is four times as clever as she is. Now, as she steps off the train, arriving to do a lecture for his students, something about her in the flesh sets him thinking. Maybe he has a chance to resolve the one remaining mystery at the heart of things . . .