Micah is a compulsive liar, and she's narrating the story. The format is something along the lines of a journal, being written after the events in question have taken place. But the journal doesn't appear to be a private journal, necessarily, and so there's definitely a question of how honest Micah is being. Especially when you get to a new chapter and she starts by apologizing for lying, and clarifying where the lies were in the previous chapter. There are chapter segments, tagged with titles like "Before", "After", and "Family history" which helps a lot in keeping track of what's going on. The event they refer to is the death of a boy who was killed, possibly murdered, and who had been in some sort of a relationship with Micah.
It feels fairly obvious right off the bat that Micah didn't kill Zach. She is horrified and traumatized by his death, and yet she's lying about many of the things surrounding his death, and often lying to the authorities. Some of these lies feel very much like a just a confused teenager - telling one story to the authorities who she has been taught to distrust, another to Zach's official girlfriend who she feels, sorry for, threatened by, and weirdly attracted to, and yet another story for her parents. But most teenagers (I think) have a tendency to be honest with the police, especially when there's a murder investigation underway. Especially when someone they loved is dead, and they aren't responsible.
Obviously there's a twist, and yet I totally missed all the hints in the first half of the book, and it took me a while to actually believe Micah once she finally revealed what was actually going on. Micah is so adept at lying and filling in those little details that make lies convincing. When I outlined the story to Sky he saw the twist immediately because I didn't include those little details.
Her unreliability makes the story fascinating. I'm still not entirely clear on some of the details of the story - specifically surrounding her younger brother. Turns out that lying about having lied about something is quite convincing too. By the end of the story you know that Micah is a liar, you've been lied to often enough that you can't just relax and trust her, and yet she is being more honest with you now than ever.
This is a lovely story, twisty and turney and totally satisfying. And way more true than if it had just been told factually without all the lies. Because lies are the foundation of Micah's life, and once you start to be able to see through the lies, and understand why she is lying and what she lies about, you're able to understand her in a way that you never could otherwise.