JK Rowling has secretly written a crime novel under the guise of male debut writer Robert Galbraith.
The Harry Potter author was acclaimed for The Cuckoo's Calling, about a war veteran turned private investigator called Cormoran Strike.
The book, published in April, has sold 1,500 copies in hardback so far.
Rowling's secret emerged after the Sunday Times wondered how a first-time author could produce such an accomplished work.'Without hype'
Rowling said: "I had hoped to keep this secret a little longer because being Robert Galbraith has been such a liberating experience.
"It has been wonderful to publish without hype or expectation, and pure pleasure to get feedback under a different name."
One reviewer described The Cuckoo's Calling as a "scintillating debut". Another praised the male author's ability to describe women's clothes.
A clue that Rowling was behind the novel was that she and "Galbraith" shared an agent and editor.
The book was published by Sphere, part of Little, Brown Book Group which published her foray into writing novels for adults, The Casual Vacancy.
There were also similarities in style between The Cuckoo's Calling and Rowling's other works.'Mature writer'
Rowling said her editor, David Shelley, had been "a true partner in crime".
Crime writer Peter James told the Sunday Times: "I thought it was by a very mature writer, and not a first-timer."
The fictitious Galbraith was supposed to have been a former plain-clothes Royal Military Police investigator who had left the armed forces in 2003 to work in the civilian security industry.
In previous interviews, Rowling has said she would prefer to write novels after Harry Potter under a pseudonym.
Another Cormoran Strike book by Robert Galbraith is in the pipeline, to be published next year.