Ella has lived with her grandmother and uncle ever since her parents died in a fire many years before. Ella and her extended family all have differing forms of synesthesia. Her grandmother sees sounds, her uncle can taste words, and Ella sees auras which tell her lots about people. So when she meets Alec and can't read him at all, she's not sure what to make of him even though she is drawn to him right away. Alec is keeping a secret - he has met Ella on purpose because he is investigating her parents' deaths which were definitely murder, not an accident. Once he reveals his true purpose, Ella has many questions which are clearly leading to danger with a killer who doesn't want her to dig into the past.
It's fine. That's about all I can say for this book. I was intrigued by the set up with the synesthesia and the fact that Ella had no inkling that her parents had been murdered, but then it just dragged on for a lot of pages without building on that momentum. Ella's loyal friends are wasted characters, only in a few scenes to mark their territory with Alec since Ella continues to trust him despite his lies and the fact that she has no idea who he is. It's pretty clear early on who the (main) villain is if you've read many mysteries. That revelation might be surprising for some less experienced readers, but even if it is a surprise, I don't know that they will be invested enough in this character to be all that shocked. In fact, now that I'm reflecting on it more, I don't even find the murderous plot plausible, especially given Ella's aura-reading skills. Perhaps that's why that storyline is not explored in more depth - because it turns out she doesn't actually see lies at all.