Felonious Fiction : EQUATION FOR EVIL,<i> By Philip Caputo (HarperCollins: $25; 488 pp.)</i>

What a state we live in, California! The ‘90s are only at midpoint and we have already seen several serial killings, mass murders, televised police brutality, race riots, the most famous murder trial in American history, a rock superstar accused of pederasty, a rapper accused of drive-by killing, rampant child molestation, spousal abuse, victimology, earthquakes, floods, fires, pestilence, pollution and, of course, plague--all of it recorded and instantly regurgitated for our delectation by an insatiable media.

What is the mere fiction writer to do? How can he or she possibly compete for our attention with this bread-and-circus that would make an ancient Roman’s mouth drop open in amazement?

Philip Caputo, one-time Beirut hostage, Pulitzer Prize-winning journalist and author of the highly regarded Vietnam novel “A Rumor of War,” has, like the good war correspondent he is, sucked in his gut and chosen to wade straight into the belly of this beast. In his latest fictional work, “Equation for Evil,” Caputo takes on most of the hot-button issues of our time--racism, random violence, disempowerment, the decay of the social fabric, even the nature of evil itself--and, I am happy to report, more than lives to tell the tale.

His story begins with the largest (fictional) mass murder in California history. In the San Joaquin Valley, Duane Boggs, a seedy twentysomething skinhead wannabe, has opened fire on a busload of Asian American children, killing or injuring almost all of them. Was he motivated by racial hatred, the desire to impress the local neo-Nazis, a drive for publicity, bad DNA or simply blind rage? Nobody seems to know, because Boggs, after committing his horrendous act, turned his weapon on himself and blew his head off. The body politic--and therefore the politicians--are distressed. What kind of madness is this? How much more can we take?

Partly to calm the public, partly to see if such events can be avoided in the future, the state attorney general orders a “psychological autopsy” to be performed on Boggs. Two men are given the assignment: Leander Heartwood, a forensic psychiatrist, and Gabriel Chin, an Asian American policeman, himself under investigation for alleged police brutality. The two are sociological opposites: Heartwood a somewhat trendy divorced intellectual who lives in San Francisco’s posh Pacific Heights, Chin a hard-nosed rural cop struggling to keep his family together. They are also philosophical opposites. Heartwood, the psychiatrist, believes that somewhere there must be a scientific explanation for villainy, that there is an “equation for evil.” Chin, the law enforcement professional, thinks that’s academic nonsense. Evil is evil, and a killer is a killer.

What ensues is a kind of police procedural novel cum metaphysical-psychological inquiry, as Heartwood tries to draw a profile of the deceased Boggs while Chin tracks clues in the traditional manner. Their investigation is long and frustrating and even threatens to become a tad boring until it takes a rather ominous turn. Chin, the dogged bloodhound, finds some troubling inconsistencies in Boggs’ suicide. It is possible that Boggs did not act alone and therefore equally possible that lurking somewhere out in the California night is another person capable of murdering a couple of dozen children in cold blood. Who knows what else he may be capable of?

Heartwood, suspicious of the success of the policeman’s conventional sleuthing, does not immediately believe Chin. But he can’t afford to disbelieve him either. What if the cop is right? Into this mix comes Mace Weathers, a handsome, one-eyed psychology student at a local college. Weathers is Caputo’s most original creation. An obsessive-compulsive neat freak and fitness fanatic, he is the apostate son of Mormon parents who has become obsessed with Buddhism and is now having an affair with a Korean girl.

Weathers wears a black eye patch because he had an eye clubbed out by some bikers who weren’t keen on his interracial dating. And yet he was also, bizarrely, a friend of the racist and almost moronic Boggs.

Caputo’s novel picks up pace as it moves toward the dramatic conclusion of a possible second mass murder. But never does the author lose sight of his philosophical interests, keeping us speculating about the old conundrum of nature versus nurture, all while we are trying to unravel the plot. “Equation for Evil” is not a perfect book--there are gulfs in our knowledge of Heartwood and Chin and some things we are told too often--but it is a thoughtful and a riveting one.

One local note: Caputo covers a lot of California in this book, some of which he likes and some of which he doesn’t. But he saves his worst opprobrium for Los Angeles, which he calls the “Vatican of Illusions.” He doesn’t, however, nominate a pope.