CANDACE FLYNT has pulled off no mean accomplishment in Sins of Omission: she has written a novel centered on a character as implacably evil as anyone you'd hope to meet, yet she has managed to make the book smart, appealing and funny. Her themes are not exactly what one would call rib-ticklers -- the temptations of the flesh, the corruption of each other, the vulnerability of love, the way deceit feeds upon itself -- and she treats them with the utmost seriousness, even to the point of ending the novel on a note that some readers will regard as "unhappy." Yet there's such an agreeably jaunty tone to the book, and such a nice undercurrent of wry self-mockery, that Sins of Omission manages to be anything but a downer.

The agent of evil is a young woman named Suzanne Cox, who works as a waitress and hostess at a pancake house in Greensboro, North Carolina. She is sexy and smart, in a feral way, and she carries a considerable grudge against the world, especially those persons in it whom she fancies to be more fortunate than she. Her rural upbringing was stunted and not without difficulty, an experience that she believes has given her a vision of life's truths denied to those whose paths have been more comfortable. "You could not pretend you had true love by decorating your apartment with hearts," she thinks. "You had to face life's facts." And it is her mission in life, she believes, to bring the cold reality of those "facts" to others so unfortunate as not yet to have glimpsed them.

Her method is random, eccentric, whimsical. Sitting in the pancake house, feeling herself "shrieking for escape," she browses in the classified advertisements and chances upon one for guitar lessons. When she rings the listed number she immediately senses that the person who answers is "a young man who had not experienced much." He is Robert Carter, a music student at the local state university, and right on the spot she decides to fall in love -- or whatever perverse emotion it is that she imagines love to be -- with him. At their first meeting she lures him into her apartment on a ruse and then crudely, irresistibly seduces him. Now begins his introduction to the "facts."

Robert, as Suzanne well knows, is newly married. His 22- year-old wife, Molly, works as an editor and writer at one of the local newspapers. She too is sexy and smart, and spunky as well, and her innocence is boundless. She is the slightly spoiled daughter of parents who live in the city's most prosperous neighborhood; she has been accustomed all her life to getting her own way, but she is also insecure and flighty and, in ways she can't always quite put her finger on, just a little bit scared. She's the perfect target for Suzanne, who sees in her the embodiment of Louise Sherrill, a privileged schoolmate whom she envied and hated; if she can't make the original offender pay the price for her transgressions, then Molly Carter will do very nicely as a stand-in.

So she begins to spy on the Carters: "Neither of them would ever believe it, but they needed her: to shake them out of their complacency, to show them how cruel the world was, to make them appreciate their future more than they had their past." She writes Robert a love letter, which of course Molly quickly sees, and which immediately alters the balance of their marriage; Robert instinctively denies that he slept with Suzanne, and Molly instinctively doubts him. The letter is followed by telephone calls at all hours of the night, anonymous letters to the Carters' neighbors claiming that Robert is to be the father of an illegitimate child, an advertisement falsely announcing a garsale at the Carters' apartment -- a long succession of intrusions on their lives. Her harassment is ceaseless, ingenious, unpredictable, and it eats steadily at the mutual and separate assumptions on which their young marriage has been based. For Molly, Suzanne is an unseen, malign presence:

"What she hated about Molly was how, like Louise Sherrill, she'd been protected all her life. How the protection had made her a coward, prevented her from developing a sense of perspective, given her no sense of what was true and what was false. On the other hand, what she liked about Molly was the same sort of intimacy she felt with anybody she'd ever spied upon: the intimacy born of watching a person behave like a human being. She had observed Molly hurt. Now she was observing her in everyday life. She would even stop by the newspaper one day and watch her work. How else could she feel but intimate?"

Under Suzanne's cruel influence, Molly gradually begins to awaken to aspects of life that previously had never occurred to her. Contemplating the possibility of Robert's infidelity, "she felt a sudden estrangement from him that she doubted would ever go away . . . Whether he'd been unfaithful to her or not, this was the first time she'd realized he had the opportunity to be. In a way, it ruined everything." Ruined, that is, her innocent assumption that she knew everything about her husband, what he thought and did, and her implicit conviction that they were always honest with each other. As doubt and recrimination increasingly come to dominate the marriage, she begins to wonder if it is lost for good. "I don't believe that what's destroyed can be built back better than before," she says. "I think you lose something forever, a sort of innocence in your belief that makes it special."

Slowly, reluctantly, Molly begins to look more closely at this beguiling man she has married, with his "tantalizing blue eyes" and his athletic build. She begins to look at herself, too, and the career she hopes to make for herself at a big newspaper in New York. All the old assumptions are called into question; in an odd, and oddly satisfying, way, Suzanne has her victory at the end.

So too has Flynt. She has taken these three people, wound them through a complex set of actual and psychological circumstances, and brought them to a conclusion that seems precisely, irrefutably right; she has brought off a number of scenes that manage to be funny and touching at the same time; she has written a solid, pleasant prose that is only slightly marred by an occasional lapse into awkward colloquialisms and that aptly reflects the youthfulness of her characters. Sins of Omission is a singularly likeable book.