[5] His work of non-fiction, Reasons to Stay Alive, was a number one Sunday Times bestseller and was in the UK top 10 for 46 weeks.

His third adult novel, The Possession of Mr Cave, deals with an obsessive father desperately trying to keep his teenage daughter safe.

It is the story of an alien who takes the identity of a university lecturer whose work in mathematics threatens the stability of the planet who must also cope with the home life which accompanies his task.

[citation needed] In 2017, Haig published How to Stop Time, a novel about a man who appears to be 40 but has, in fact, lived for more than 400 years and has met Shakespeare, Captain Cook and F. Scott Fitzgerald.

[10] Reasons to Stay Alive won the Books Are My Bag Readers' Awards in 2016 and How to Stop Time was nominated in 2017.

[11] In August 2018, he wrote lyrics for English singer and songwriter Andy Burrows's music album, the title of which was derived from Haig's book Reasons to Stay Alive.

[12] In 2020, Matt Haig released his novel The Midnight Library about a young woman who is unhappy with her choices in life.