By Jean Hanff Korelitz

Farrar Straus Giroux. 504 pp. $25

When we think of genre fiction--Agatha Christie's mysteries or Louis L'Amour's westerns--we tend not to think of great writers but of writers who were great at their respective genres. Even great writers sometimes dabble in genre (under the pseudonym Edgar Box, for instance, Gore Vidal tried his hand at mysteries), but as a rule they're slumming. Generally, reading a pop romance or a thriller by a writer who can really write is like eating food of inferior quality prepared by a four-star chef. It may taste better than usual, but still what's the point?

To be entertained, of course, and to be pulled compulsively through the pages. The aim of literary fiction, by contrast, is to slow readers down on the march through a book; to compel them to stop and savor an image, a scene, a theme or a phrase. The so-called "literary thriller" is, therefore, an uneasy hybrid. "The Sabbathday River," a new novel by Jean Hanff Korelitz, is a case in point.

Fairly satisfying as a thriller--in some ways, reading it is like reading a movie--it is only partially successful as literature. And that's not all Korelitz's fault. The writing, while uneven, sporadically rises to a level it can't sustain, in part because of the demands of the thriller's pace and plot.

At its best, Korelitz's prose is fine indeed, and demonstrates her deep sympathy for her protagonist, Naomi, who has recently parted ways with her husband, Daniel. Together, the two of them came as young adults to New Hampshire, where Naomi founded a collective devoted to empowering local women by finding a market for their handcrafted goods. Now, with her marriage on the rocks, she discovers the corpse of a murdered baby in the river, and Naomi's life and assumptions are called into question.

Living in small-town New Hampshire, Naomi is isolated by her politics and her Jewishness, among other things. She "had always considered herself a good Jew, given that, in her view, a good Jew was a person who did good things and happened to be Jewish." Living at what feels like "the farthest edge of the Diaspora," she gets caught up in a murder case that leads her to wonder if Abraham failed the biblical test he is normally thought to have passed by preparing to slay his son Isaac at the behest of his God.

Her neighbors are all too willing to blame a sexually liberated young woman, Heather Pratt, for murdering her baby. When Naomi sides with Heather against the town, she becomes even more of an outcast. As usual, Korelitz writes at her best about what her heroine is feeling. "Perhaps the world would go on like this, Naomi thought. Perhaps this was how lives were actually lived, like great swirling teacups in a child's amusement-park ride, one circle tearing around within a larger circle, but never actually making any progress. Perhaps it would all one day just stop, and she would climb out, dazed and dizzy, to see where she had got to."

Korelitz manages to present Heather's murder trial suspensefully, though there is an odd foreshortening of the preparatory maneuvering of Heather's attorney, a newcomer in town named Judith Friedman. In the universe of the thriller, where the plot must whisk by, there isn't time to prepare witnesses before they give their testimony.

It feels true, if a bit familiar, that Heather comes under suspicion because of her sexuality, and Naomi, too, because of her differentness. The dialogue is mostly good. When Judith's sister, Rachel, says, "Mom would die if she could see us," Judith quickly answers, "Mom did die."

In the end, however, "The Sabbathday River"--like many a thriller--feels overly contrived and is disappointingly easy to figure out in advance. One hopes for an ending that won't strain credulity, but also to be surprised when confronted with the truth of whodunit. Above all, one hopes not to be disappointed by the climactic revelation, and that's where "The Sabbathday River" stumbles most seriously.