The plot can be thin, a little meandering at times, and relies a bit on sudden bouts of exposition.
HOWEVER 
It's a great read. The prose is wonderful without being flowery. The tone is a great mix of ethereal, slightly detached, and beautifully caring; it really feels like it's being told by a ghost with little connection to the living. 
It can be unbearably tense at times. Just about every scene with The Smiling Man had me practically chanting "oh no oh no oh no." 
My only real issue is that we don't see enough of/about the villain to get a real sense of the stakes. It felt like she was pushed aside a bit too much and we were never really given an idea of how bad things would be if she were to succeed. 
Overall, I really enjoyed this book and will definitely be getting the sequel.