By Jonathan Kellerman

Bantam. 468 pp. $19.95

Jonathan Kellerman has made it. He's up there. We can no longer call him a child psychologist who happens to write mysteries. He's a crossover hit, a mystery novelist who has won huge mainstream success.

In six novels, Kellerman has chronicled the adventures of Alex Delaware, an independently wealthy child psychologist living in Southern California. Delaware's involvement with troubled youngsters not only leads him to the mystery genre's requisite explorations of violence, sex and social types, but also lets Kellerman show how innocent children are exploited -- sometimes without devious intent -- by selfish parents and our manipulatory, materialistic society. At the core of the Delaware novels is a bitter comment on man's inhumanity to children.

"Time Bomb," Delaware's latest adventure, begins with a schoolyard sniper. Before 19-year-old Holly Burden can injure any children with her father's unwieldy rifle, she's gunned down by the bodyguard of slimy liberal politician Gordon Latch. Latch, we learn immediately, was making a surprise visit to the Nathan Hale Elementary School to counter the presence of his hot-tempered conservative rival, Samuel Massengil.

Delaware is brought in by his sidekick, Los Angeles police detective Milo Sturgis, to counsel the panicked schoolchildren, most of whom are from poor, minority families. Delaware is immediately disgusted at the politicians, who were on the scene to take sides over the neighborhood's school busing controversy. Delaware becomes simultaneously curious about the sniper's motives and sexually attracted to the school's comely young principal, Linda Overstreet.

Unlike the conventional street-smart detective, Delaware employs his skills as a therapist to wring the truth from duplicitous supporting characters. Like a psychoanalytic Santa Claus, Delaware knows who's naughty or nice. He has an almost unbelievable talent for asking just the right question to launch the most stubborn psychological type into a long, soul-searching soliloquy. And types they are: Everyone seems to have a psychological tic. The sniper's technology-obsessed father is revealed as an egocentric narcissist, her brother is orally fixated, and the politicians are kinky sado-masochists.

Even Linda Overstreet, Delaware's love interest, has an Electra complex over her domineering father. Though Delaware tries to refrain from using his skills to seduce her, he senses her vulnerability and just about shoves her into bed.

The parade of psychological types grows a bit tiresome, as does Delaware's misanthropic snobbishness about Southern California. Most detective heroes are social misfits in one way or another but Delaware seems to be a victim of his own analytic blindness. With the exception of his good buddy Milo Sturgis and Linda Overstreet, Delaware loathes or finds ridiculous just about everybody he encounters over the age of 21.

It's okay for Delaware, a professional with a refined sense of integrity, to bristle at the "new age" hokum of the fraudulent child psychologist Lance Dobbs, a repugnant oaf who seems drawn from Kellerman's personal experience. But it's a cheap shot for Delaware to despise the shallowness of so many characters when his personal life, as he describes it, is about as deep as a dishpan. Buying art, listening to the bland jazz-pop of Spyro Gyra and Kenny G, and enduring inept service at restaurants indicates a man who consumes life, but does not savor it. Next time out, Kellerman should consider putting his hero on the couch: Alex Delaware, for all his integrity, should lighten up.

Of course, it's hard to lighten up when mysterious cars follow you, a pair of bogus FBI agents knock you out and kidnap you, and a demented Hitler-to-be tortures your buddy and promises you and your girlfriend similar treatment. Yes, it's tough being a competent child psychologist these days.

Or is it that Kellerman the author doesn't think a probing portrait of family pathology makes a strong enough story?

I suspect that the latter is the case. What starts out as an inquiry into trampled innocence becomes a well researched but pathetically cliched revelation of neo-Nazi white supremacists pulling political strings. The climax is ludicrous: a rerun of that silly formula in which the villain, who only wants to kill the good Dr. Delaware as horribly as possible, permits Delaware to babble on and on about the villain's dastardly schemes. This leads to a page torn from a James Bond screenplay, in which the chattering Dr. Delaware and bloodied detective Sturgis make a desperate escape from the Nazi lair, dodging exploding bombs and bullets fired by heavily armed uniformed henchmen who can't hit a slow-moving target at point-blank range.

This stuff makes for mindless entertainment, but also cheapens the story's human element. Kellerman has a passionate concern for the plight of misunderstood children, and faith that, as fragile as they seem, children have the innate strength to survive the cruelties inflicted on them by adults. On this alone Kellerman could have built a moving, important story.

Instead Kellerman has fashioned a bomb that, when it does go off, makes a lot of smoke and fire, but has little lasting impact. The reviewer is the author of the mystery novel "Under the Boardwalk."