The multiverse is real. From Earth Zero, there are people trained by the Eldridge Institute as traversers: people who can safely go to the other 379 Earths and gather data to help influence the economic security of their home. "Safely" means they do not have living doppelgangers on the other Earths, which means the least privileged can go. This includes Cara, who grew up in the Wastes in Ashtown, and is now on her way to citizenship in the affluent Wiley City. She doesn't fit in either place. When Cara is sent to a world where her counterpart has died under mysterious circumstances, she finds a new realm that contains a secret—one that will have force her to make choices that will not only reveal some of her own past and determine her future security, but will also affect the multiverse. VERDICT This exciting debut is intelligently built, with clever characters, surprise twists, plenty of action, subtly detailed worlds, and a plot that highlights social and racial inequities in astute prose.—Kristi Chadwick, Massachusetts Lib. Syst., Northampton