Exquisite. Unique. Haunting. At its core, What's Left of Me examines the very fabric of humanity through Eva and Addie, two souls inhabiting the same body. Surrounding this thought-provoking premise is a meticulously created world where two souls are born to one body but only one survives early childhood, where the isolated Americas seek to destroy hybrids - those who have failed to settle. A superb tale that I read in one sitting, this book left me pining for more.Eva is trapped in the body she shares with Addie, the dominant soul. She and Addie live in fear that someone will find out their secret - that they are hybrid. Perhaps it is because the story is narrated by Eva, but I got the sense that Eva should have been the dominant one. She is smart and quick thinking, and while Addie doesn't function well without her, Eva does fine on her own. Addie also came across as a little self-centred, but I imagine she is terrified that one day Eva will become dominant and she will be trapped in her body (like Eva is now), so I guess some of her actions are warranted.For most of the novel, in fact, until the last few chapters, I viewed the world building as weak. We are led to believe that the Americas are on lockdown - having cut all ties with the outside world - to prevent the onset of wars and general depravities caused by hybrids. The dystopian element comes into play quickly - citizens of the Americas are taught that the rest of the world is burning, tearing itself apart because the hybrid problem has become uncontrollable. But it's never explained why hybridity would cause these issues, and there isn't much information given about how the Americas have ensured that their society is largely devoid of hybrids. But there are a few big reveals near the end that solve the mystery (and introduce new ones in its place), which prove that the world building in this book is, in fact, incredibly strong.Kat Zhang's mastery is evident in the way she has created the dual natures of her characters, and then made the readers believe it through the prose. The differences between the two souls of a hybrid are subtle: facial expressions and gestures, likes and dislikes, but they are believable and relatively easy to separate. Although it is initially confusing that Eva, narrating the story, does so by referring to our hands and our voice, and is always describing what Addie is doing (because she, herself, can't do anything) I quickly adjusted and was able to enjoy the story and its unique execution.This book left me breathless, and I am eager to continue reading about Eva and Addie's adventures. A beautiful, creative blend of quality science fiction and terrifying dystopian, What's Left of Me will be enjoyed by fans of both genre and is sure to impress the most discerning of readers.