Sales of Robert Galbraith’s first two books have reached 1.5m copies across print, audio and e-books, according to the publisher.
Little, Brown said that sales of The Cuckoo’s Calling (Sphere), the first novel written by JK Rowling under the pseudonym Galbraith, has sold 1m copies in the UK across all formats.
The Silkworm (also Sphere), released in 2014, has sold over half a million copies in the UK including e-books and audio downloads.
Through Nielsen BookScan The Cuckoo’s Calling has sold 385,000 physical copies, and The Silkworm 139,000 print copies.
Career of Evil, the third book in the series, will be published on 20th October.
The series is currently being adapted for a new television series for BBC One, produced by Brontë Film and Television.