My own unapologetic opinions on books and writing.
This is an interesting premise. I guess it's targeted to younger readers but it's Gaiman and he does most things well.
The trouble with Gaiman is that I can't help comparing him to Gaiman. The bar is pretty high! I wouldn't say this is his best, but it's certainly not his worst and it's headed for the 4 star range. It's just turning toward explanations. What is it with me and Mystery plots recently? I don't generally seek them out because they drive me nuts, wanting to know.
I'm enjoying the read though.