A Thousand Pieces Of You by Claudia Gray

After her scientist father is murdered, a resourceful young woman uses his prototype device to chase his killer across multiple parallel universes. As she inhabits alternate versions of herself and the people she loves, she uncovers a conspiracy that forces her to confront shifting loyalties, dangerous consequences, and the difficult choices between different lives and loves. The hunt becomes a test of identity, sacrifice, and the cost of altering fate.

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