ANDREW H. VACHHS has written quite an extraordinary thriller in Flood (Donald I. Fine, $17.95). Imagine a New York where the streets are worse than mean, they're positively depraved. The hero Burke is a private detective (sort of) with an engineer's approach to survival. He lives with a huge mongrel named Pansy in an apartment fortified like a bank vault; he drives a $40,000 Plymouth loaded with more gadgetry than James Bond's Aston Martin. His friends include a transvestite prostitute, a mute Tibetan fighting machine named Max, a panhandler called the Prof (short for Professor or Prophet, no one's sure which), an electronic wizard who lives underground beneath a pile of junked cars, and a doctor who doubles as the secret leader of an Hispanic revolutionary group.

In his first case, Burke takes on a client named Flood, a martial arts expert, searching for the man who raped and killed a little girl. Together they make quite a team, something like Modesty Blaise and Willie Garvin in a novel by Celine. For this is a very violent book, and Vachhs never flinches from the horror: he includes a sickening description of a snuff movie, chilling (yet comic) portraits of would-be soldiers of fortune, and a convincing look at the underworld of child pornography. Indeed, he veers close to the didactic in some of his rants about the slime who prey on little kids -- but who can blame him? Vachhs himself is an expert on child abuse and juvenile delinquency. His is not a pretty world, and he has no use for conventional pieties to excuse atrocity.

Virtually every survivalist fantasy of urban life finds its place here -- Burke the vigilante, with his superhero comrades; the city as concrete jungle; civilization constantly assaulted by fiends in human form. Vachhs' language is wry, Chandleresque, and laced with authentic details about the methodology and gadgetry of crime:

"I sell a lot of identification, mostly to clowns who want the option to disappear but never will. The stuff looks pretty good -- all you need are some genuine state blanks, like for drivers' licenses, and the right typewriter. IBM makes a special typing element. . . . They call it an OCR element and you can't buy it over the counter but this is something less than a significant deterrent to people who steal for a living. I have a complete set in the office."

Flood's only fault -- assuming, of course, one is not dismayed by its draconian social views -- may be its length: it sacrifices a tight artistry for a rambling panorama of damned souls. In the end, though, Burke does find the child-killer, and Flood fights for her life in ritual combat. The Greeks in Oxfordshire

MUCH ADMIRED in England, Peter Levi's Grave Witness (St. Martin's, $11.95) depicts the adventures of a classical archeologist who becomes involved with Greek pottery, shady art dealers, an eccentric English antiquarian, his beautiful niece (the love interest), and a variety of crimes including murder, theft, kidnapping, and an elaborate con game. Certainly, there is enough here to make a thrilling novel and learned one in the style of Edmund Crispin and Michael Innes. The only trouble is that Levi tries to blend the two, and doesn't quite pull it off.

For instance, the hero Ben Jonson (a peculiar ostentation) opens his story with a portrait of his academic archenemy, one Frowser: "The reference books credit Frowser with a critical volume called Sentiment and Metaphor. I have heard it said that his chapter on Gertrude of Wyoming opened the eyes of the learned world to new delicacies in the shorter longer poems of the earlier middle century." Funny yes, but a rather familiar kind of academic humor. A similar wanness characterizes the tidy love affair and rather unthreatening adventures. Jonson is knocked on the head at the shop of a dealer in artifacts, he is kidnapped twice (once would have been enough), his involvement with Joy proceeds far too smoothly, and there is an obtrusive use of foreshadowing, even of the old-fashioned "Had I but known" convention for which Mary Roberts Rinehart was notorious.

Still, Grave Witness partially redeems itself with eccentric characters -- the mysterious vicar Dr. Stoup, his dotty sister, the John Aubrey-like antiquarian Ralph Iggleby who discovers Greek treasure in his backyard, various officious policemen. The writing is certainly fluid and competent, as one would expect from Oxford's current professor of poetry, himself a well known classical scholar. In short, this struck me as a mildly diverting mystery, but not half so clever or thrilling as it would like to be. California Classic

IN ALL its elements T. Jefferson Parker's Laguna Heat (St. Martin's, $15.95) resembles the classic hard-boiled California novel, especially the version mapped out by Ross Macdonald. Homicide detective Tom Shephard is the wounded hero, seeking to heal himself from a broken marriage and the memory of the night he was forced to kill a teen-aged boy. Laguna Beach is the sunny, artistic community, rotten with ancient secrets beneath its smile and Izod sportswear. Several disparate crimes -- the death of Tom's mother when he was a baby, the drowning suicide of a prominent club owner in 1951, and the horrible murders, by burning, of leading citizens -- all come together to form part of a single, ominous pattern.

As Pope would say, all this has oft been said but ne'er so well expressed. For Parker transmutes these familiar themes into a powerful, meticulously orchestrated novel, one where every note, every chord serves to build toward a violent climax and a moral coda. The story begins with the invstigation of a small-time gambler burned to death and ends with Shephard confronting a madman in the jungles of Mexico, but the path from the one to the other is perfectly logical, even as it runs by the Surfside country club, a drive- in converted into a church, a gay bar, Folsom State Prison, and the cool waters of Diver's Cove.

Each character in Laguna Heat could walk away into the real world. A widow passes the surplus years alone in a bedroom decorated entirely in white. Shephard's father Wade, once suicidal and alcoholic with despair over the death of his wife, abandons police work to become a pop evangelist, and his sermons ring true to anyone who's listened to Robert Schuller or Rex Humbard. There is even a spot-on cameo of the police chief, a socialite administrator whose devoured all the management and vocabulary manuals:

"'I don't want to know who your suspects are, what your leads are, or what your hunches might be. Professionals work best sans encumbrance. I simply want quotidian assurance -- for the mayor and myself -- that you are doing everything possible to make an arrest. . . . A tourist town is only as good as its image. The only thing worse than murder would be a giant shark eating bodysurfers off Main Beach. You remember Jaws, don't you?'

'A fine film.'

'My favorite part was the storytelling scene in the boat. The lost art of verbal painting. But I'm getting sidetracked, Shephard. My brain is on a right-side tack today.'"

A fine novel, Laguna Heat will linger in the memory even after all the puzzle's pieces are finally in place. A Canterbury Tale

SUSAN KENNEY -- like a good many crime-story writers -- is something of a double threat: Her previous whodunit about Roz Howard, Garden of Malice, was a hit with mystery readers, while her first novel In Another Country earned the kind of reviews young writers dream about. She is certainly someone to watch, in both genres.

In Graves in Academe (Viking, $15.95) Roz Howard is hired by Canterbury College to replace one of its professors who has died under unusual circumstances. Roz agrees to take over his course -- a survey of early English literature, with concentrations on Beowulf, Chaucer and the Renaissance dramatists -- even though she must leave her beloved Alan in Scotland. Soon she finds herself embroiled in academic in-fighting: the Dean wants to eliminate freshman composition, which will weaken the English department's power, while the English faculty is adamant about getting rid of fraternities. It seems that fraternity pranksters may be involved in recent assaults on female students, and may even be responsible for the death of a college co-ed.

Roz buckles down to her course work, but nonetheless finds herself attracted to a sculptor named Thor, the macho Dean, and a mysterious student named Rick. Then one night someone tries to poison three professors; a dramatically successful murder soon follows. Is there a lunatic on the loose? And what is his motive? Naturally, Roz works her way toward a solution, but not before she finds herself in mortal danger.

For all its scholarly sleuthing, Graves in Academe possesses a couple of serious faults. The killer struck me as pretty obvious, despite a last-minute attempt to deflect attention to another suspect. But the real annoyance was Kenney's idiosyncrasy of calling her Canterbury professors Franklin, Manciple, Knight, Parsons. Aha, I thought, how clever, if cutesy, to name the suspects and victims after Chaucer's pilgrims! But Roz, who is teaching Chaucer, fails to notice that the entire English faculty could have stepped out of the The Canterbury Tales, while Kenney the author never uses this oddity in the solution to the crimes. Altogether annoying -- especially for readers who like their mysteries neat. Still, this is an engaging book, with nice touches of humor, academic satire, and psychological portraiture.

Michael Dirda is mysteries editor of Book World.