It is an interesting premise. One body with two souls. One has to settle, one has to fade away... 
 What's Left of Me by Kat Zhang tells us the story of such a world where everybody starts off with two souls and by the age of ten, the more dominant soul settles in while the other fades away. We are told that in Hybrids, where both souls survive past the settling age, are dangerous. When either one of Eva and Addie did not settle in by the age of ten, it turned heads, caused whispers and caused people to shy away from the whole family. Finally, at the age of twelve, Addie was declared healthy while Eva faded away. Only, Eva held on desperately for a chance to be able to be in control. While they try their best to keep it hidden, they meet a pair of siblings who are also hybrids. Lissa/Hally and Devon/Ryan try to show Eva how to take control again. But the secrets they keep and the choices they make could potentially lead to death of both Addie and Eva. What will they do and how far will they go to save each other? 
 The concept of twin souls in a body caught my attention immediately and as such I found the blurb interesting enough to pick up the book as soon as I could get my hands on it. I was curious about how it worked before the 'settling'. To have each soul control the body part-time must be confusing. What did the other soul do then or how does it exist? Even after settling in, how can the second soul still exist? If the second soul hangs on, does it mean that the first soul is not strong enough or just that the second soul is stronger than expected? In any case, both Eva and Addie's characters are brilliantly developed. It was easy to love them both. Honestly if I were to choose one of the two, I don't think I could. Different as they are, they are both equally essential to the story. 
 The story simply sucked me in from the very beginning. We are told the story from Eva's point of view and her voice feels so genuine and unique. Seriously, how would any of us feel to have to let go of our twin? Yeah, it's heartbreakingly beautiful.