Lawrence Sanders is a prolific as he is skilled. "The Third Deadly Sin" is his 12th novel since "The Anderson Tapes" appeared in the early '70s, and it reinforces his position as one of the most consistently satisfying "entertainment" novelists writing in America today. It is the third in his "Deadly Sins" series featuring a Manhattan policeman -- chief of detectiveds Edward X. Delaney, not retired but still very active -- who is as interesting as the odd criminals he has been encountering.

Besides crime (about which he has also written powerfully and with great variety in "The Anderson Tapes" and the "Ten Commandments" series), Sanders has ventured into science fiction ("The Tomorrow File"), revolutionary politics in Africa ("The Tangent Objective" and "The Tangent Factor") and even the world of theater ("The Marlow Chronicles," a novel whose structure is cleverly modeled on that of a well-made play). In all of these genres, he has performed with distinction, inventing characters of real substance, involving them in consistently interesting plots and telling of their adventures in a style taht combines ease and elegance. "The Third Deadly Sin" may be his best novel so far -- but with Sanders one often has the feeling that his latest novel is his best.

Unlike what he has done with the commandments, Sanders seems to be going through the deadly sins in the order of their traditional listing. Having handled pride and covetousness already, he has not reached lust -- a fictional motif as timeworn as it is absorbing, one would think. And he has managed to come up with an original variation on the old theme.

A crazed killer stalks Manhattan, taking victims in a curious pattern once every lunar month, leaving them in their hotel rooms (they are always visitors, not residents) naked, and their throats cut and with a frenzied array of stab wounds around their genitals. "The Hotel Ripper" (a term quickly invented by the New York papers) has the police baffled, not only because the killer is clever and very careful, but because there is something wrong in the pattern. Multiple homicides following a compulsive pattern are not unknown, although they are relatively rare, but the killers in this kind of crime, from Jack the Ripper to Son of Sam, have invariable been male -- at least the ones who have been identified.

The assumption that this killer, too, is a man involves the New York police in a lot of running down flind alleys before Delaney is lured, temporarily and not at all reluctantly, out of retirement. While he works his way toward the truth, with a combination of hard, routine work and inspired hunches, the reader watches in fascination -- not to discover who the murderer is but to enjoy the working-out of the investigative process. This is a police procedural novel, not a whodunit, and the real narrative questions are what notivates the crimes and whether and how the killer will be caught. There is no question about the identity of the Hotel Ripper after page 43, when Zoe Kohler is shown in action:

"Handling the Swiss Army Knive like a dagger, she plunged the big blade into the left side of his fat neck and sawed back toward her.

"He made a sound, a gargle, and his heavy body leaped convulsively from the bed. Blood spouted in streams, gobblets, a flood that sprayed the air with a crimson fog. It soaked the bed, dripped onto the floor."

In spite of all the gore in this passage, Zoe is not your run-of-the-mill sex-crazed killer any more than "The Third Deadly Sin" is an ordinary, blood-soaked cheap thriller. She is (or seems to be) totally colorless -- an average, reasonable competent and not over-pressured Manhattan office worker, almost invisible as she walks down a crowded street and impossible to remember if you happened to notice her at all. There are certain advantages in this, of course, for one who is taking up murder as a serious hobby.

Zoe has other advantages -- neatness, a natural shyness, a methodical and painstaking personality, a sense of moderation -- all of which are reflected in her modus operandi. But habits do affect our personalities, and the habit of murder (along with an obscure physical ailment) finally changes Zoe's personality and leads to her undoing. At first, her victims tend to be rather distasteful creatures, and the murders can be construed as a crazy, puritanical crusade. There is pathos, too, in the way she reads the newspaper accounts of her crimes and the police investigation, almost as though these bits of paper prove and justify her existence. But later, she becomes less fastidious in her choice of victims, less careful about leaving clues. She is still almost pitiful, even when she is shedding blood, because her illness -- even more than her murders -- becomes a symbol of the reader's mortality.

In chapters that alternate between Zoe's point of view and Delaney's, Sanders shows the reader both sides of the crime and generates an evenhanded empathy for everyone involved. The final chapter gives the book an unexpected but thoroughly prepared denouement which brings this detective story up to the borderlines of authentic tragedy.