Jhumpa Lahiri’s third book, Unaccustomed Earth (Knopf, $25), is a collection of eight short stories, each of which packs the punch of a novel.  In the title story, Ruma debates the merits and disadvantages of asking her aging father to live with her growing family; in another, Sudha watches her brother throw away his life in the grips of an addiction he cannot control; in a third, Amit considers how his Bengali upbringing and values are so thoroughly different from those of his American wife, and how that affects their relationship. Lahiri deftly spins her satisfying stories in a way that not only makes you identify with the memorable characters, but also builds toward a stunning conclusion that will haunt you long after you close the book.