If you happened to be one of the 1,500 or so people who bought debut novelist Robert Galbraith’s detective story The Cuckoo’s Calling before this past weekend and noticed that the writing style seemed familiar, it was. While the novel’s publisher, Mulholland Books, had previously claimed it was written by a former member of the Special Investigative Branch of the Royal Military Police, the Sunday Times revealed over the weekend that it was actually penned by Harry Potter creator J.K. Rowling. The author explained in a statement that she assumed the pseudonym in order to “publish without hype or expectation.” She called it a “liberating experience” and “a pure pleasure to get feedback from publishers and readers under a different name.” Now that her secret’s out, sales have skyrocketed 507,000%.