The space between worlds

Multiverse travel is finally possible, but there's just one catch: no one can visit a world where their counterpart is still alive. Cara's parallel selves happen to be exceptionally good at dying: from diseases, from turf wars, from vendettas they couldn't outrun. On this Earth, Cara has survived--and she's reaping the benefits, thanks to the well-heeled Wiley City scientists who ID'd her as an outlier and plucked her from the dirt. Now she's got a new job collecting off-world data, a path to citizenship, and a near-perfect Wiley City accent. When one of her eight remaining doppelgangers dies under mysterious circumstances, Cara is plunged into a new world with an old secret. What she discovers endangers not just her world, but the entire multiverse. -- adapted from jacket