Steamy Sex, a Little Murder and Intrigue--It’s All Here : BOOK REVIEW : BLOODSONG <i> by Jill Neimark</i> ; Random House; $20, 304 pages.

“I’m in love with a murderer,” announces a young woman named Lynn on the very first page of “Bloodsong,” thus summing up the conceit at the heart of Jill Neimark’s first novel--the confessions of a young woman who is crazy in love with a dangerous man.

Lynn Hershey is a 29-year-old free-lance writer who lives amid the crush of humanity in New York City and yearns for a truly intimate encounter with another human being. And so she places a personal ad that seems guaranteed to draw a fair number of wrong numbers--”You’re a mystery, a messenger, an invitation, a wanderer, my half-brother. . . .”--and, sure enough, the number she draws is a man with blood on his hands.

Kim Beckett is “a gorgeous mistake,” a welder who lives in a sleazy Times Square hotel, but he turns out to be a sexual sorcerer with a faintly sinister aura: “One of those still-waters-run-deep guys from the Midwest,” as one of the women in Kim’s life puts it.

Lynn is obsessed with solving the mystery that lurks somewhere inside Kim’s brooding soul, and--as we see in a series of lush and lyrical flashbacks--she discovers that Kim was caught up in some trouble in the cocaine trade down in Puerto Rico. As she digs ever deeper into Kim’s life, she meets Katie, the woman who beguiled Kim and the man who became Kim’s victim. And Lynn comes to understand that the act of homicide was vastly more complicated than she first suspected.

Now Kim may be a murderer--and Lynn may find a certain kinky thrill in submitting to his sexual mastery--but we are carefully instructed that Kim is not one of those creepy serial killers who stalks women or a homicidal nerd who takes an Uzi to a fast-food restaurant. No, Kim is quite an elegant and even elevated sort of killer, and what Lynn manages to discover about the circumstances of the crime is intended to reassure us that Kim is not such a bad guy after all.

Still, Lynn goes on and on about the fact that her lover is a killer, and it’s clear that she finds the whole idea a big turn-on: “ Murderer , you call yourself, the sound succulent and hideous,” Lynn rhapsodizes. “Say this: He killed a man. Say it.”

And “Bloodsong” is one turned-on book, a story so charged up with sexual energy that Lynn literally quakes and quivers. The steamier moments are too explicit to quote here, but “Bloodsong” is not merely an exercise in titillation. Neimark writes about sexuality of the mind and body with genuine intimacy, engaging candor and a dark but ecstatic eroticism.

“I’m already shaking with that sweet rage of the body,” Lynn exults in a moment of lovemaking. “My pelvis a sponge of blood. The blood singing under my nerves. Nerves whine and shudder. It’s as if he’s striking some primordial membrane.”

Neimark is taking a certain risk when she pumps up the rhetorical volume of her prose to such a high pitch. She is never understated or circumspect when she has something to say about the sexual encounter between man and woman. And, at some moments, “Bloodsong” goes over the top, as if Neimark simply could not resist the temptation to show off her gift at phrase-making.

“Kim leans toward me and touches my lips with his, in the most excruciating never-ending kiss,” Lynn says. More often, though, Neimark succeeds in carrying it off. “Bloodsong” might have turned out to be just another trash novel in the hands of a writer less earnest or less gifted than Neimark, but she pours so much passion and so much poetry into her first novel that the story literally begins to sing.