No Christopher Nolan film was adapted from James Ellroy’s novel The Black Dahlia.
The question highlights a common mix-up involving Nolan’s 2002 film Insomnia. Insomnia is a remake of the 1997 Norwegian film of the same name, directed by Erik Skjoldbjærg, rather than an adaptation of an Ellroy novel.
James Ellroy wrote The Black Dahlia, a 1987 crime novel inspired by the unsolved murder of Elizabeth Short. Brian De Palma later directed a film adaptation of that novel in 2006, but Christopher Nolan was not its director.
Nolan’s films include original screenplays, comic-book adaptations, and adaptations of other works, such as The Prestige, which was based on Christopher Priest’s novel. Separating these source materials helps avoid attributing Ellroy’s book to Nolan.