IN OCTOBER OF 2014, HARRY STYLES WENT FOR A HIKE  in Los Angeles, and on the way back, made his driver pull over so he could puke by the side of the freeway. Paparazzi took photos, which circulated online and in tabloids. One fan visited the location, marked it with a sign reading “Harry Styles Threw-Up Here,” and posted a picture to Instagram. Five years later, Kaitlyn Tiffany, One Direction fan, staff writer at The Atlantic, and author of Everything I Need I Get from You: How Fangirls Created the Internet as We Know It (MCD/Farrar, Straus and Giroux, $18), sought out the spot on a Harry