A Taste for Death by P. D. James (Knopf: $18.95; 459 pp.) : Live Flesh by Ruth Rendell (Pantheon: $15.95; 272 pp.)

Women who write crime novels well are almost inevitably described as successors to Agatha Christie, the once and future queen of the field. Both Ruth Rendell and P. D. James have been identified as heiresses-apparent, and they are both by a considerable distance the best practitioners of the crime novel now working in England.

But Dame Agatha was a puzzle-maker rather than a plot-maker. The ingenuity of her schemes and the shrewd and mischievous misdirection by which she concealed her villains and withheld her denouements give her works--which are also astonishing in their profusion--a timeless and universal popularity that no one appears likely to equal, ever.

Rendell and James offer different gifts: literary grace of a high order and the ability to give full dimensions to both character, relationship and environment. While Rendell first made her name with tidily plotted police procedurals, her larger reputation now rests on her suspenseful studies of aberrant psychology, of which her new book, “Live Flesh,” is a mesmerizing example.

She has a chill-inducing ability to get inside thoroughly wacko characters and give their obsessions and their madnesses a terrible and inevitable logic. The reader is carried along by a fascination and pity that override the revulsion.

In “Live Flesh,” her central figure (protagonist is too kindly a word) is a rapist named Victor Jenner who, by a skein of inadvertences, has held a young woman hostage and shot a policeman and left him paraplegic.

Now Jenner is out of prison and drawn, by a fateful combination of guilt and resentment that is itself a form of madness, toward the policeman and his new life.

Chief among the needs of the crime writer is to make credible the links of coincidence and the follies of mind on which the story must hang.

Is it conceivable that victim and victimizer could become friends, however edgy, and even a romantic triangle with the victim’s girlfriend?

The real suspense is that for a moment, like a roller-coaster car poised at the top of the parabola, Jenner might go either way, surrendering to the decency of the detective and his lover or plunge into a charade of self-deception and acting out that must be fatal.

Rendell is unusually prolific: 25 novels and four collections of short stories so far. But she appears to improve with experience, setting herself more difficult challenges right along. Rendell writes very coolly, yet there is a felt pity if nothing like a sentimental compassion for her emotionally wounded subjects.

Once again, P. D. James is pushing patiently at the presumed limits of the crime story. “A Taste for Death” runs to nearly 500 closely printed pages, twice the length of most mysteries. And it says something for her popularity (fed by the miniseries made of “Death of an Expert Witness” and now “Shroud for a Nightingale”) and for the rising popularity of mysteries generally that “A Taste for Death” is a full selection of the Book of the Month Club.

Two men, a harmless old vagrant and a Member of Parliament lately resigned from a cabinet post and his seat, are found knifed to death in the vestry of a London church. The finders are a sweetly wistful elderly woman who does the altar flowers and an artful dodger of a boy who brings her gifts he has obviously nicked from markets.

It is a baffler, and James’ ongoing sleuth, Chief Inspector Adam Dalgliesh, is doubly involved because he knew the MP slightly, knew him as a diffident, unhappy, superconscientious man who had lately undergone a kind of religious revelation (which led him to sleep in the consoling quiet of the church).

There are, it will need no saying, innumerable complications: a nice mistress, a cold and faithless wife and her lover, a smarmy brother-in-law, an estranged daughter with an unattractive far-left lover, an uncommunicative chauffeur, an imperious mother safeguarding an elaborate family past.

Still it takes a lot of texturing to fill those 459 pages, and James makes the most of her eye for architectural detail (she invents a whole house by Sir John Soane) and for the nuances of feeling and shadings of atmosphere.

She writes with precision and elegance. There are character sketches, lines of perception that ask to be remembered, and perhaps read aloud. Kynaston, the police surgeon “had given up general medicine for pathology at registrar level because he could no longer bear to watch human suffering . . . now he applied his diagnostic skills to the unrepining dead, whose eyes couldn’t implore him to offer hope, whose mouths could no longer cry out.”

Dalgliesh, visiting the MP’s home, “had the sense, as he often did in the house of the recently murdered, of a thin denuded air, a voiceless presence.” Dalgliesh himself, the poet-detective who hasn’t been able to write poetry in recent years, is a more complicated figure than most, brusque and reserved, an intellectual who displays neither his erudition nor his feelings, which, behind the impassive facade, are real enough.

In puzzle stories, crimes tend to have taken place and are then re-created in endless rehashes, leading to a denouement that is as orderly as a sit-down dinner.

In both Rendell and James, things still happen. In James, the child who knows too much is endangered; the vicar grapples with an intruder in the dark church, the culprit holds a room at bay. In Rendell, there is a last fateful, bloody charade, madness in full command, whipping through the preliminaries to a last confrontation.

The Rendell, I think, is much the better book: well-paced, well-written, original and startling, engrossing in its examination of a character at once hateful and pitiable.

Glorious as the texturing of “A Taste of Death” is, there is the ultimate sense that it hides a rather banal little mystery, complicated in its details yet in its motivations and its solution as superficial as any in the melodramas that “Perry Mason” churned out on television week after week. The politician is an interesting figure about whom a “straight” novel could certainly have been written. It’s a shame we didn’t get to know him in life.

The line between the crime story and the straight novel is never hard and straight, and the best crime writers leave an indelible picture of their moment in time, as writers as different as Margery Allingham and Raymond Chandler have, and as Rendell and James certainly do. Dame Agatha’s vicarages and house parties are a very long way away.