I need to start by noting that the protagonist has an imaginary friend who she talks to in her head and who has an entire life separate from hers. Not like Harvey or Hobbes, who exist alongside their companions, but more like having a best friend you can only talk to in your head and who lives on another continent and/or world. And who probably doesn't exist and who doesn't entirely think you exist either. This is completely awesome. As soon as this was introduced, I was all "why have I never seen this before? Can I use this in a story without plagariazing Brennan? Surely this cannot be the first story to use this device!" There must be some portal fantasy or something that also did it.
So there's that, which I loved. The cast as a whole is well-written and likeable while remaining distinct. There's a lot of silly, entertaining banter. The book largely revolves around one key relationship, which is intense and compelling. I greatly enjoyed the first half of the story, liked the next third or so, and cannot even make sense of the ending. As in wait what why is this happening what wait that is the END? You are stopping? There? What
I kinda wish Brandon Sanderson would give Sarah Rees Brennan lessons on How to Write a Good Ending. v_v
This is book one of I-don't-know-how-many, so maybe the sequel(s) will explain some of the what? I am willing to give the next book a shot whenever it comes out, anyway. I'm giving this book a 7, though. Because .... really ... what?