I thought this was a great young adult horror story. The kids are likeable, and credible in a horror movie sort of way. Frequent horror movie references, on the other hand, are one of the book's weaknesses. I'd have like the story to stand on its own without being propped up by such frequent mentions. A few were fine for flavor, but Liparulo ladled on too many.
On the other hand, the story was engaging and fun. I wanted to see what was happening, and what the source of the mystery was. The ending was both too quick and too sudden. It's one thing to leave readers wanting more. It's another to basically put up a cliffhanger billboard saying "Buy the next book!". (You have to be half over the cliff to see the billboard. By then it may be too late.)
All in all, a fun read, and I may pursue the next in the series, if it's reasonably priced.