PD James, creator of Adam Dalgliesh and one of the most acclaimed living writers of detective fiction, sets out in this tactful and engaging book some thoughts on her art. She suggests that the detective genre is differentiated from both mainstream fiction and the generality of crime novels "by a highly organised structure and recognised conventions", and by the requirement that it "enshrine a mystery and its solution", a definition loose enough for her to draw comparisons with canonical works such as Jane Austen's Emma and Charlotte Brontë's Jane Eyre.

Indeed, James believes that the genre has been unfairly stigmatised by critics, and is as worthy of academic attention as any other kind of writing. She is not at her most persuasive when arguing this point, since the criticisms she summarily refutes are on the whole of her own formulation. But as a personal (and gleefully partial) survey of the highlights of English detective fiction over the past 200 years, her book offers much that will enlighten and entertain.

James traces the history of the genre from its 19th-century origins in the work of Charles Dickens and Wilkie Collins, through its coming of age in the stories of GK Chesterton and Arthur Conan Doyle (her musings on the practicalities of Holmes and Watson's living arrangements are very funny) to its apotheosis in the "golden age" in England between the wars, as exemplified in the work of Agatha Christie and Dorothy L Sayers, and the alternative offered by the "hard-boiled" style of American authors such as Raymond Chandler and Dashiell Hammett. The book ends with a look at the current state of detective fiction, which James regards as fairly healthy.

James's style is every bit as elegant here as it is in her fiction: she presents her views with a modesty that makes it hard to take exception to them, coupled with an intellectual vigour that makes it impossible not to take them seriously. At almost 90, with more than 20 books behind her, she remains a writer of tremendous energy and intelligence, and this essay comes as no mean addition to her oeuvre.