"So Yesterday" is a young adult novel written by Scott Westerfeld. It follows the story of Hunter Braque, a teenager who navigates the fast-paced world of fashion and trends in New York City. The plot revolves around Hunter's experiences with his friends and their quest to uncover the mystery behind a missing designer. The book explores themes of consumerism, identity, and the fleeting nature of trends. As Hunter and his friends delve deeper into the fashion industry, they confront the pressures of staying relevant in a world where what is "in" can change overnight.