The Hypnotist - signed, lined & dated

Lars Kepler is the pseudonym of husband and wife team Alexandra Coelho Ahndoril (born 1966) and Alexander Ahndoril (born 1967), authors of the Joona Linna series. With nine installments to date, the series has sold 15 million copies in 40 languages. The Ahndorils were both established writers before they adopted the pen name Lars Kepler, and have each published several acclaimed novels.

The Joona Linna series follows Joona Linna, Detective Superintendent at the police's National Operations Department, Saga Bauer, an Operational Superintendent at the Swedish Security Service, and Erik Maria Bark (in The Hypnotist and Stalker), a trained psychiatrist and psychotherapist specialised in psycho-traumatology and disaster psychiatry.

In autumn 2015, Lars Kepler's sixth novel was published in Sweden, a stand-alone novel entitled Playground.

On 18 February 2020, Albert Bonniers Förlag announced that Lars Kepler was the best-selling author of the decade – Swedish or international – in Sweden, across all categories, genres and formats.