Harry Potter author JK Rowling has secretly written a crime novel under a false name.

The writer has won plaudits for The Cuckoo's Calling, about a war veteran turned private investigator called Cormoran Strike.

Rowling used the moniker Robert Galbraith for the book, which was published in April.

The true identity of the author was only revealed at the weekend.

She 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."

The Cuckoo's Calling has sold 1500 copies in hardback so far.

The book was published by Sphere, part of Little, Brown, which published her last novel, The Casual Vacancy.

A spokesman for Waterstones said: "This is the best act of literary deception since Stephen King was outed as Richard Bachman back in the 1980s.

"Before The Casual Vacancy was published, the general suspicion was that JK Rowling might write a crime novel: turns out we were right! This is a wonderful summer surprise for readers and booksellers everywhere."

One reviewer described it as a "scintillating debut".

In the hours after Rowling was named as its author, it shot up the bestseller charts.

It was listed as the third biggest seller on Amazon.co.uk yesterday, having entered the top 100 only the day before.