This essentially a middle grade thriller, set at Christmastime. 

The book is very fast paced and fairly engaging, with decent characters. Unfortunately I had significant issues with the plot. There is one aspect of the mystery which almost the entire plot of the book hinges on, which makes absolutely no sense when you discover it. More than one character makes stupid decisions for seemingly no reason except to facilitate the next stage in the plot.

Overall probably a decent read for a child - it would be good introduction to the thriller genre - but not quite a satisfying book for an adult reader.