Her detective novels include:
- Cover Her Face (1962) (introducing her Scotland Yard detective Adam Dalgliesh)
- A Mind to Murder (1963)
- An Unsuitable Job for a Woman (1972) (introducing her female sleuth called Cordelia Gray)
- Death of an Expert Witness (1977)
- Death in Holy Orders (2001)
Many of P.D. James' mystery novels take place against the backdrop of Britain's vast bureaucracies such as the criminal justice system and the health services, arenas in which James honed her skills for decades starting in the 1940s when she went to work in hospital administration to help support her ailing husband and two children. Two years after the publication of Cover Her Face, James' husband died and she took a position as a civil servant within the criminal section of the Department of Home Affairs. James worked for government service until her retirement in 1979, and her many years of experience within these bureaucracies add a complex stratum of insider's knowledge to her writing. Her latest work, Death in Holy Orders, displays an insightful grasp of the inner workings of church hierarchy.
It has been noted by many critics that James has upgraded and expanded the entire genre of mystery writing; and that many of her books, especially the police procedurals starring Dalgliesh, the poetry writing detective, fit the mainstream novel criteria as much as they do the detective genre. James' strengths are characterization and her ability to construct atmosphere and stories rich in detail.