Restless girls, dissatisfied wives, and wistful old women populate Alice Munro’s sparkling 10th collection, set, as usual, in her native Canada. Munro’s world is governed equally by luck and the sudden, surprising willfulness of her beautifully drawn protagonists. In the aptly titled ”Chance,” Juliet, a brainy young school-teacher on a cross-country train ride, is approached by an unappealing middle-aged man who suggests they ”chum around.” Munro excels at capturing the inner life of an accommodating good girl on the brink of rebellion: Juliet has often felt ”surrounded by people who wanted to drain away her attention and her time and her soul. And usually, she let them.” Not this time. In a moment of unprecedented self-assertion, she coolly rebuffs the stranger’s overtures, moving to the observation car to read in peace. And there she meets the man she will eventually settle down with. Runaway doesn’t break new ground — and it lacks the continuity and power of Munro’s 1979 masterpiece, The Beggar Maid — but any new compendium of Munro’s wise, delicate, and insightful tales is a treat.