“This is your copy of Advanced Potion-Making, is it, Potter?”“Yes,” said Harry, still breathing hard.“You’re quite sure of that, are you, Potter?”“Yes,” said Harry, with a touch more defiance.“This is the copy of Advanced Potion-Making that you purchased from Flourish and Blotts?”“Yes,” said Harry firmly.“Then why,” asked Snape, “does it have the name ‘Roonil Wazlib’ written inside the front cover?”Harry’s heart missed a beat. “That’s my nickname,” he said.”