Judy and the Beast (Goosebumps Slappyworld #15)

"Judy Glassman lives with her brother, Kenny, and father, Noah, in a village at the foot of Evil Rock. Every winter, Kenny accompanies their dad up to the mansion at the top of the mountain to assist the rich, eccentric Grendel family with their house repairs. But this year, Judy convinces her dad to let her come too. Judy has heard whispers about the Beast of Evil Rock -- a half-human creature who stalks the crags. And she's determined to find out for herself if it's true. Will Judy discover the secret of Evil Rock before the Beast finds her first?"--Publisher's description.