He has few friends and often clashes with colleagues, but his work and skill are so widely known and respected that he is considered a specialist, leading him to sometimes consult on cases in other cities and countries.

A common focus of the novel series is Hole's struggles with alcoholism and depression, as well as how his mental health suffers as a result of his morally questionable actions and the brutal nature of the crimes he investigates.

The novel series eventually shows Hole recognizing the harmful nature of his work and increasingly problematic behavior, prompting him to leave the police force.

[4] Despite this, later novels show Hole continually finding reason to return to Oslo and assist new criminal investigations, despite his own initial reluctance and the protests of his loved ones.

[5][6] Critics liken the personality of Harry Hole to those of the famous literary detectives such as Sherlock Holmes, Hercule Poirot, Jules Maigret, and Nero Wolfe.

His encounters with assassins, corruption, and serial killers throughout the novels often strengthen his cynical views and his desire to escape reminders of his experiences and traumas.

Bjarne Møller, head of the Oslo Police Department, often shields Hole from being fired, believing he is a brilliant detective and vital to certain investigations.

Others in the police department whom he comes to trust as friends include Beate Lønn and Bjørn Holm (both in the forensics division), Katrine Bratt (a Bergen detective who helps secure specialist information), and Gunnar Hagen (Harry's former senior officer prior to Phantom).

Kaja Solness, a new Norwegian Crime Squad officer, asks him to return to Oslo to help investigate a possible serial killing.

The seventh novel in the series, The Snowman, was adapted as a film in 2017 and starred Michael Fassbender[10] as Harry Hole, with Rebecca Ferguson, Charlotte Gainsbourg, Ronan Vibert, Val Kilmer and J.K. Simmons.