She's a niche writer, but it's a niche that keeps expanding for Rebecca Yarros. Onyx Storm, her latest novel in the "romantasy" genre is now the fastest-selling adult fiction title in 20 years, reports the New York Times, citing stats from Circana BookScan. The book is the third in Yarros' five-book Empyrean series, which is set at a military academy in a fantasy world that features dragons. Onyx Storm sold 2.7 million copies in its first week, and Yarros now holds the top three spots on the New York Times best-seller list. "It doesn't feel real, none of it does," Yarros told nearly 2,000 fans—many adorned in Empyrean-themed costumes—who packed into an auditorium in St. Paul, Minn., this week.