First born : a novel / Will Dean.
(Book)

"Molly Raven lives a quiet, structured life in London, finding comfort in security and routine. Her identical twin Katie, living in New York, is the exact opposite: outgoing, spontaneous, and adventurous. But when Molly hears that Katie has died, possibly murdered, she is thrown into unfamiliar territory. As terrifying as it is, she knows she must travel across the ocean and find out what happened. But as she tracks her twin's final movements, cracks begin to emerge, and she slowly realizes her sister was not who she thought she was and there's a dangerous web of deceit surrounding the two of them."--Amazon.com.