Scream School (Goosebumps Series 2000, No. 15)

You hold in your hand the key to a shadow world of shivers and screams. Take a step away from the safe, comfortable world you know. Unlock the door to terror. There's always room for one more in! THE NIGHTMARE ROOM! Sam Waterbury has just started at his new school. And something isn't right. There's a strange green imp terrorising the school -- and it doesn't like new kids. Especially cheeky ones. Looks like Sam's just walked into! THE NIGHTMARE ROOM!