The original novel was set in New England, with an American team of psychic investigators. The storyline was changed, to fit the movie's production in England, with British actors playing the investigators.
The unsettling tales of Emeric Belasco's acts of debauchery and evil at Hell House were loosely based on stories involving occultist Aleister Crowley. Crowley, whose home from 1899 to 1913 was named "Boleskine" also used the Pseudonym "Lord Boleskine.
Early in the film, in her and her husband's bedroom, Ann Barrett is seen holding the novel "Sentimental Education" by 19th century French author Gustave Flaubert. The novel was no doubt deliberately chosen for her to hold by the filmmakers since much of the novel is about passion, sex, and desire, making it fit in well with the highly sexualized and erotic nature of much of the film. It also foreshadows her later scenes and hints at her repressed sexuality.
Writer Richard Matheson toned down the graphic violence and more intense sexual scenes of his novel to give the screenplay for the film a more brooding atmosphere.
The old books that Ann Barrett sees lined up in the cabinet are titled, from left to right; Obsessive Acts And Religious Practices by Sigmund Freud, The Worship of Priapus by Richard Payne Knight, The Psychology of Sex by H. H. Ellis, Sin And Sex, Conation Volition, Sex And Celibacy by T. Long, The Anatomy of Abuses by Phillip Stubs, Phallic Worship and Auto Erotic Phenomena In Adolescence by K. Menzies.