Crime novel 'Cuckoo's Calling' has taken a giant leap to reach the number spot on Amazon UK's best selling list from a lowly 5,075 after the name of its real author was outed. Robert Galbraith turned out to be the pseudo-name of Harry Potter series author, J.K. Rowling.

"For a title that isn't even in our top 5,000 to shoot to number one so quickly is almost unheard of," Darren Hardy, books manager at Amazon.co.uk, told Reuters.

As a debut novel of a new author on the publishing block, Cuckoo's Calling had sold around 1,500 copies in hardback. The demand for the book has surged rapidly post revelation of the real author, which has left publisher Little, Brown and bookstores in Britain unprepared to meet the sudden demand.

Hardy told Reuters that this dramatic rise in sales of the book meant, "The Cuckoo's Calling has established itself as a contender to become one of the biggest-selling books of the summer."

"With book shops genuinely caught out and lacking stock (surely the biggest sign this wasn't some fascinating long-con), anyone who wanted a copy of The Cuckoo's Calling was going to have to go digital," Ewan Spence writes in Forbes.

Reagan Arthur, publisher of Little, Brown said in a statement that "A reprint of the book is under way and will carry a revised author biography, which reads 'Robert Galbraith's is a pseudo-name of J.K Rowling'."

J.K Rowling said in a statement, ""I 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 from publishers and readers under a different name."

Published in April, the book had received good reviews and the revelation of the real author is now going to make it a profitable, commercial success. In the book, Cromoran Strike, a war veteran turned private investigator, investigates the suicide of a young model in London. Little, Brown has said that it intends to publish a second book, next summer.

"And to those who have asked for a sequel, Robert fully intends to keep writing the series, although he will probably continue to turn down personal appearances," J.K. Rowling said.