From Helen Schulman, the acclaimed author of the New York Times bestseller This Beautiful Life, comes another "gripping, potent, and blisteringly well-written story of family, dilemma, and consequence" (Elizabeth Gilbert)

Amy Reed works part-time as a PR person for a tech start-up, run by her college roommate's nineteen-year-old son, in Palo Alto, California. Donny is a baby genius, a junior at Stanford in his spare time. His play for fortune is an algorithm that may allow people access to their "multiverses"-all the planes on which their alternative life choices can be played out simultaneously-to see how the decisions they've made have shaped their lives. Donny wants Amy to be his guinea pig. And even as she questions Donny's theories and motives, Amy finds herself unable to resist the lure of the road(s) not taken.