One of my favorite of the Goosebumps series--both as a kid and now that I find myself reading them to my own offspring. 
 I maintain that the first dozen or so of these books were the best written. 
 In this particular installment, the author manages to address the concept of trusting your gut instincts--supplying fantastically eerie consequences to ignoring them. There're also lessons to be had in regards to the dangers of peer pressure, over-competitiveness, and messing with forces one doesn't understand. 
 A cautionary tale, to be sure. And one that sticks firmly in the imagination.