His previous novel Mayflies (2020) won the Christopher Isherwood Prize, and was adapted into a two-part BBC television drama of the same name.

O'Hagan was born in Glasgow City Centre in 1968,[1][2] of Irish Catholic descent, and grew up in Kilwinning, North Ayrshire.

[2] In 2003, his next novel Personality, which features a character similar to Lena Zavaroni, won the James Tait Black Memorial Prize for fiction.

In 2012, O'Hagan worked on a theatrical production about the crisis in British newspapers, entitled Enquirer, with the National Theatre of Scotland.

His essay, entitled "Ghosting",[11] published in the London Review of Books, gained significant media attention because of his description of Assange's character and strained relationships with past and present colleagues.

In September 2011, the National Theatre of Scotland presented The Missing as a play adapted by O'Hagan and directed by John Tiffany at Tramway, Glasgow.

"[22] The Guardian called the work "an arresting, genre-defying work – part speculative memoir, part Orwellian social reportage" that "induces the kind of shock he [the author] must have experienced..."[23] In December 2022 BBC One showed an adaptation of Mayflies starring Martin Compston, Tony Curran, and Ashley Jensen.

He has travelled to Sudan, India, Malawi and Mozambique and has joined fellow ambassadors Ewan McGregor, Ralph Fiennes, James Nesbitt, Martin Bell and Jemima Khan in campaigning for Unicef.

[citation needed] In August 2017, O'Hagan gave a speech at The Edinburgh International Book Festival, where he declared that he had become a supporter of Scottish independence.

[29] O'Hagan was selected by the literary magazine Granta[30] for inclusion in their 2003 list of the top 20 young British novelists, and his novels have been translated into 15 languages.