Which book did J.K. Rowling publish first under the pen name Robert Galbraith?

The Cuckoo’s Calling was the first book J.K. Rowling published under the pen name Robert Galbraith.

The novel appeared in 2013 as a contemporary crime story rather than a fantasy novel. It introduces Cormoran Strike, a former military investigator who becomes a private detective, and Robin Ellacott, who joins his agency. Strike investigates the apparent suicide of model Lula Landry.

Rowling’s identity was initially kept secret, allowing the book to be judged without the immediate expectations attached to the Harry Potter name. A Sunday Times investigation later identified similarities between the novel and Rowling’s known writing, and Rowling confirmed the authorship.

The later Galbraith novels continued the same detective series. The Silkworm is the second, Career of Evil the third, and Lethal White the fourth, so those titles cannot be the first Galbraith publication.