Margaret Atwood’s The Robber Bride is inspired by “The Robber Bridegroom,” a wonderfully grisly tale from the Brothers Grimm in which an evil groom lures three maidens into his lair and devours them, one by one. But in her version, Atwood brilliantly recasts the monster as Zenia, a villainess of demonic proportions, and sets her loose in the lives of three friends.