Mary McScary by R.L. Stine
Meet Mary McScary! She doesn't say boo. She says "BOOOOOOOOO!" Mary spends her days being scary. She scares her mum, her dad, her pets, and even a balloon! But Mary has met her match when her cousin Harry McScary comes to visit. He's not afraid of anything, until Mary finds a way to give Harry the scare of his life... A wildly funny new picture book by the award-winning talents behind GOOSEBUMPS and ARTHUR.