It's the book Mum told Harry not to write. If you're squeamish, look away now. If you want wizards, ginger beer or secret gardens, you're out of luck. But if you're looking for ferrets, bad magic and crotchety old ladies, congratulations! Buckle up for Harry and Charlie's most outrageous adventure yet as they're off to a birthday party like no other. Things are going to get messy - don't forget the wet wipes!