By the time Todd wrote Chapter 90—of an eventual 295 chapters—her novel-in-progress had been read more than 1 million times. Multiple literary agents reached out to her, but she dismissed them as “crazy people,” figuring no legitimate professional would seek out One Direction fan fiction. Readers composed sequels starring After’s characters, uploaded video homages to the book, and—finally convincing Todd that she might have something big on her hands—chatted as Tessa and Harry on Twitter role-playing accounts. Seeing that, “I was like, ‘Holy shit,’ ” Todd once recalled. Representatives from Wattpad, which had never had such a blockbuster, contacted Todd and offered to help connect her with publishers. Before she flew to meet with Wattpad’s staff at the start-up’s Toronto headquarters, she overdrafted her bank account to pay for her passport.

Since then, Todd’s After series has been published as four volumes by Simon & Schuster in a six-figure deal, earned a spot on the New York Times best-seller list, been read nearly 1.6 billion times on Wattpad, been translated into more than 35 languages, and been adapted into a feature film, which Todd is co-producing, and which co-stars Selma Blair. (For the print and movie versions of After, Harry Styles has been renamed Hardin Scott.) On a recent book tour through Europe, cheering fans swarmed train stations waiting for Todd to disembark.

Her franchise has also helped establish Wattpad as a hub for young people drawn to its interactive approach to the written word. The site’s 65 million monthly users, who are overwhelmingly female and under 35, spend an average of 30 minutes a day reading authors who range from middle schoolers to Margaret Atwood. Building on its collaboration with Todd, Wattpad has helped hundreds of stories be adapted into books, TV shows, or films through deals with HarperCollins, NBCUniversal, Sony Pictures Television, and others; the site says it can forecast Gen Z hits and trends with far greater accuracy than industry gatekeepers acting on their gut. (Wattpad predicts that mermaids and cannibals are poised for stardom.) Netflix’s The Kissing Booth, described by an executive at the streaming company as “one of the most-watched movies in the country, and maybe in the world,” began as a Wattpad story written by a 15-year-old.

Todd sees no basis for the idea that young people have soured on books—a favorite complaint among those worried about kids these days. During my recent visit to her trailer on the film set of After, in Atlanta, she told me that an “insane” number of teachers had written to thank her for inspiring a love of reading. After discovering Tessa and Harry’s obsession with authors like Charles Dickens and F. Scott Fitzgerald, their students devoured classic literature. Todd recently lent her star power to several authors who in fan-fiction circles might be seen as underdogs: Her Italian publisher released special-edition translations of Anna Karenina, Pride and Prejudice, and Wuthering Heights prominently branded with Todd’s After-inspired logo (two interlocking hearts that form an infinity sign). “OMG PRIDE AND PREJUDICE IS LIKE AFTER,” tweeted one reader. “ANNA you are so smart I can’t even.”