What is the title of J.K. Rowling’s first published book written for adults under a pseudonym?

J.K. Rowling’s first published book written for adults under a pseudonym was The Cuckoo’s Calling.

The crime novel was published in April 2013 under the name Robert Galbraith. It introduces Cormoran Strike, a private investigator who examines the death of supermodel Lula Landry. Strike works with Robin Ellacott, who becomes an important recurring character in the series.

The book initially attracted attention as an apparently new author’s debut. Rowling’s identity was revealed several months later, after linguistic analysis and investigative reporting connected the novel to her. Sales rose sharply once the connection became public, but the novel remained associated with the Galbraith series rather than being republished under Rowling’s primary name.

The title is sometimes confused with The Casual Vacancy, which was Rowling’s first adult novel but appeared under her own name in 2012. The Cuckoo’s Calling is specifically the first adult publication to use the Robert Galbraith identity.