Dark Harvest by Norman Partridge (2007)

Dark Harvest
It’s Halloween night and every teen boy in town has been locked up for five days.  Tonight they are released, ready to do battle with a legend come to life: The October Boy—born in a cornfield and made of candy, vines and a pumpkin head.  The boy who succeeds in killing him gets to leave town and the competition is fierce, but who are they truly fighting?  

Partridge creates a suspenseful, chilling novel and beautifully evokes the feeling of autumn and Halloween, while telling a truly original story with well-drawn characters.