All in all, the plot is good.
R. L. Stine has always bugged me with the way he writes- even at 8, I still thought the books were rather empty. It's a good quick read that will tide you over for a day if you've finished with your book and can't get to the library untill the next day.
Carnage is (as usual for Stine) gruesome and frequent, but (some my find this a good thing) not very descrbed or focused on.
Another thing about this book that annoys me is the 'Hand of God' ending-there were no previous hints on who the killer was.
Final line-Good plot, Okay writing, 3/5