“Innocent Blood” is a London crime novel by the grand dame of British detective fiction Phyllis Dorothy James, or as she is better known, P.D. James.

The words on the back cover of my paperback edition (picked up in a second-hand bookshop in Alexandra, New Zealand) says it could be read “as a mainstream novel and a considerable one”.

“As a crime novel it is a peak of the art,” the back cover goes on to say, a little awkwardly.

This is high praise, but it is richly deserved, because this is a fine book, demonstrating P.D. James’s complete command of the English language and why she has rightly been called the ‘Charles Dickens’ of crime fiction.

The plot of “Innocent Blood” is quite simple, yet unconventional for a crime novel since both the murderer and the ‘murderer-to-be’ are known to the reader early on and instead of being mysteries that must be solved, are devices to explore the lives and motivations of the two key characters.

And yet there are still some very surprising twists and an unexpected ending.

The rape and murder of a child 10 years ago brings the two lead characters together.

First there is Philippa Palfry, adopted at a young age by upper class academic Maurice Palfry, who finds out, after she turns 18, who her real mother is – a child murderer called Mary Ducton

Mary Ducton is soon to be released from prison after serving a 10 year sentence for the murder.

Philippa is an intelligent, somewhat cunning and striking looking young woman with golden hair and high cheek bones, who has aspirations to be a writer.

She is determined to know her real mother – her only true family – even after she finds out the truth of her awful past.

Rather than have a holiday in Europe before beginning her studies at Cambridge, as had been her original plan, she finds a short-let flat in London to live with her mother for a few months so they can get acquainted.

Then there is the story of Norman Scase, father of the child murdered by Mary Ducton. He is a plain, small. methodical man, who has lived an unremarkable life as a bookkeeper. He quits his job once he knows that Mary Ducton is to be released from prison in order to fulfil a promise made to his dying wife that he will kill the woman who murdered their daughter.

The novel explores Philippa’s relationship with her mother as well as her ties to her adopted father and his unhappy second wife. It follows Norman Scase as he carefully and with a steely resolve, plans the murder of Mary Ducton, while also delving into his unhappy childhood as an “ugly” child in Brighton.

The action takes place over about two months in London in the summer.

P.D. James is an unusual crime writer in the sense that while the plot-lines are very strong, she takes detours in the storytelling to focus on small details such as a minor character’s motivation and past history and rich descriptions of buildings and places: the London underground clogged with people, a bad meal eaten by Philippa in a restaurant on Edgeware Road.

In this way she creates a living, breathing world that the reader can disappear into.

The writing is meticulous, beautifully crafted and rich in detail.

A short extract demonstrates P.D. James ability to describe a scene and unsettle the reader.

One day, by accident, before Norman Scase has exacted his revenge on Mary Ducton, he comes across Philippa and her mother, “the murderess” while taking a blind woman he has met to the park:

“It was then that Philippa saw the man. He had come up the sloping path from the lake, a small, spectacled, grey-haired man… His glance fell on her, their eyes met and instinctively, and out of the lazy pleasure of the moment, she smiled at him. The result was extraordinary. He stood transfixed, eyes widened, in what seemed a second of incredulous terror. Then he turned abruptly away…Philippa laughed aloud. He was a plain, ordinary man, not repulsive and surely not so plain that no woman before had ever spontaneously smiled at him.

The novel is awash with these beautifully observed moments. Journeys on the London Underground. The tourist crowds at Oxford Circus. The stalls at a London market opening in the morning.

I have read a number of interviews with P.D. James, and in them she emphasises the importance of a good plot and story. Often, she says, working out the plot of her novels will take longer than writing them. She also says that she always writes with the reader in mind and so does not wish to disappoint.

And she certainly does not with “Innocent Blood”.

The book, published in 1980 was a huge commercial success and made her a wealthy woman.

She later received a peerage in the House of Lords and became known by the imposing title of the Baroness James of Holland Park.

She has won over a dozen literary awards for her crime fiction, most of which is in the traditional style of the detective novel (her protagonist is an unorthodox detective called Adam Dagleish) and many of her books have been adapted for television – though not Innocent Blood – it would make an exceptional movie.

Despite the success, wealth and title she has obtained, P.D. James reveal herself to be a delightfully down-to-earth women who in one newspaper interview professed her love of discovering things and learning new facts.

She once told a journalist she re-read a book of hers before a lecture (she does not normally re-read her books) only to discover, to her amusement, the murderer wasn’t whom she thought it would be.

If you are looking for an unconventional, exceptionally good crime novel, then “Innocent Blood” should be top of your pile.