BOOK REVIEW / NOVEL : Riveting Thriller Doesn’t Let Up on Tension and Violence : KISS THE GIRLS <i> by James Patterson</i> ; Little, Brown; $22.95, 451 pages

“Kiss the Girls” is one of two thrillers on the current bestseller lists by authors named Patterson, and the two rival Pattersons--James and Richard--are running neck and neck in the blood-and-gore sweepstakes.

It’s James Patterson, author of the bestseller “Along Came a Spider,” who’s at work in “Kiss the Girls,” which features his trademark hero, the tough but sensitive detective Alex Cross, on the trail of not one but two bloodthirsty serial killers. And, as we see once again in his latest book, James Patterson deals in much rougher trade than such fellow thriller writers as Richard North Patterson (“Eyes of a Child”).

Patterson’s Alex Cross is one of those hard-boiled but softhearted detectives who seem to proliferate in postmodern mystery fiction. He’s got a psychology Ph.D., but works as a police detective in Washington, D.C. He’s a dedicated single father and sensitive guy; when not on the trail of various slavering killers, he plays “blues, soul and a little fusion” to entertain his young children.

“I loved these times with my kids more than I loved all the rest of my life put together,” Cross declares in one of many sentimental moments in an otherwise hard-edged thriller.

One of the two serial killers whom Cross chases in California, from Melrose Avenue to Big Sur, is the dapper homicidal maniac known in the newspaper headlines as “the Gentleman Caller” because he always leaves a bouquet of flowers by his victims after sexually assaulting them and cutting off body parts as souvenirs.

The other killer is the ultra-creepy sexual psychopath whom we know as “Casanova.” As he stalks and closes in on a series of beautiful young women in the Carolinas and points south, Casanova fancies himself to be the world’s greatest lover--but the objects of his “fantasy du jour” end up bound, drugged, tortured and sometimes dead.

“I’m like a killer shark, with a human brain, and even a heart,” says the cracked Casanova, who likes to wear masks that change according to his mood, which is almost always foul.

The predators strike close to home when Cross’ beloved niece, known by the nickname “Scootchie,” disappears from Duke University, where she’s studying law. So when Cross sets out to rescue her, he is working off something more volatile than the average cop’s desire to collar a bad guy.

“I bowed my head low,” says Cross at the scene of her abduction. “Finally, I wept for Scootchie.”

The emotional investment becomes even greater when Cross falls in love with one of the other victims, a lovely young doctor who is depicted as so heroic that we cannot believe she will actually die.

As it turns out, a good many unpleasant people are to be found in these pages, and not only the obvious ones. Doctors, journalists and Southern cops come off as especially odious in Patterson’s eye. And Patterson is not reluctant to describe the sexual torment that the two maniacs practice upon the bodies of the young women strewn through these pages. Indeed, the violence is explicit and unrelenting, and one passage in particular, which involves a snake with its mouth sewn closed, a milk enema, and a woman hung by ropes from the rafters, was quite literally stomach-turning.

Patterson adopts the all-too-familiar shorthand of pop fiction, using the titles of movies and television shows to signify emotions and to set an ominous tone. On Page 288, for example, as the murderer wields a cleaver over his latest victim, Patterson writes: “Shades of Hitchcock’s ‘Psycho’ and also ‘Frenzy.’ ” On Page 291, as yet another murderer comes to the mind of yet another victim, Patterson repeats himself: “Images of ‘Psycho’ flashed through her mind. . . .”

If Patterson’s book follows a strictly by-the-numbers formula, it is a formula that works undeniably well. Writing in short, snappy, 2 1/2-page chapters that tick like a time bomb, always full of threat and tension, he hastens us through the parade of horribles toward the big bang of an ending. By then, we may be more relieved than surprised by the climax, but it’s tough to put down the book until we get there.