The Nightmarys by Dan Poblocki
Timothy and Stuart have been best friends since grade school, but lately Stuart has been getting kind of obnoxious and negative. When Timothy accidentally chooses the new girl, Abigail, as his project partner Stuart is furious. He won’t talk to Timothy and begins tormenting Abigail, who just wants to be left alone by everyone. Then Stuart really starts freaking out. At swim practice he insists a monster is in the pool waiting for him. Then he practically drowns. Timothy and Abigail have also been experiencing some weird phenomenon – all of which is connected to their deepest fears. A little digging and they find out it all started with Abigail’s grandmother, her best friend’s disappearance, an evil professor and a powerful curse that has travelled down through the generations to Abigail herself. To unravel the curse Abigail and Timothy must find an ancient jawbone and destroy it before all of their worst fears come to life.