An extremely modest-selling detective tale called The Cuckoo's Calling is now rocketing up bestseller lists after a weekend revelation the book is actually the work of Harry Potter creator J.K. Rowling.

Writing under the pseudonym Robert Galbraith (purportedly a retired investigator penning his debut novel), the blockbuster Scottish author released The Cuckoo's Calling in the U.K. and U.S. in April. It sold just 1,500 copies in the past few months.

However, after a weekend Sunday Times report unveiled Rowling as the author, demand is surging for the novel and members of the British book industry — including publishers who turned the manuscript down and critics who passed it over — have been left red-faced.

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

The Cuckoo's Calling follows Cormorant Strike, a troubled former war vet turned private detective investigating the death of a supermodel in London. The book was published by Little, Brown, which also released Rowling's first novel for adults — The Casual Vacancy — to incredible hype and ultimately mixed reviews in 2012.

The publisher said it was "looking forward to publishing Strike's next installment in summer 2014."

Rowling confirmed she was indeed the author and noted that she had hoped to keep the secret longer because it had felt liberating.

"It has been wonderful to publish without hype or expectation, and pure pleasure to get feedback under a different name," she said in a statement to the Times.

It isn't the first time Rowling has modified her name to publish her work: she pitched the Harry Potter series using her initials rather than her proper name (Joanne) because she initially worried about her gender influencing potential readers.

Like her record-breaking Harry Potter novel series, The Cuckoo's Calling was turned away by several firms before finally being released. Orion Publishing's fiction editor Kate Mills was among those who admitted to rejecting the tale, posting about it via Twitter.

Cathy Rentzenbrink, a reviewer for trade magazine The Bookseller, revealed that she had read one chapter before dropping The Cuckoo's Calling. However, Publisher's Weekly and the few other outlets that did review the novel gave it positive write-ups.

It was suspicion about how a first-time novelist could write with such confidence and maturity that led the Sunday Times to investigate.

A former single mother and welfare recipient, Rowling is now one of the world's best-read writers and among the U.K.'s wealthiest people. She made her success with Harry Potter and has sold more than 400 million copies of the teen wizard novels around the globe.