"So Long at the Fair" By Christina Schwarz Doubleday ($24.95)

Jon Kepilkowski is known as a straightforward, trusty guy -- except that lately he has been cavorting with someone other than his classy wife, Ginny.

Wracked with guilt -- he loves his wife after all -- he swears off his mistress, Freddi, a young sexy co-worker at the advertising agency where he works.

His life hangs in the balance as Ginny comes closer to discovering what she knows in her gut, and this gripping new novel follows one July day in the life of a marriage teetering on the brink. Schwarz writes with perfect pitch on the cadences of marital tensions, the casualness of cruelty, the allure of something new -- "a life unsullied by compromise and untethered by promises."

In some ways, the book is a headlong pager-turner about one day in the present.

But this is Christina Schwarz, the gifted author of the best-selling "Drowning Ruth," a book that weaves a web of deceit from secrets of the past. Once again in this new novel, the past stalks the present.

In this case, the past is a complex revenge plot that unfolds in the summer of 1963 in the same small Wisconsin town where Jon and Ginny grew up. Marie, Jon's domineering mother, manipulates everyone around her, orchestrating a dark drama.

This ominous subplot comes out in dribs and drabs -- little vignettes, interspersed among the narrative and written in italics.

Schwarz is like a juggler, throwing up various vignettes in the air, including an obsessed man who stalks Freddie.

But at times she seems to be juggling too much. The 1960s subplot seems a little contrived and thuds to the ground.

No matter. Her main storyline is so good that you can excuse her.

Even though Jon vows to stop his affair, he has a fight with Ginny the morning of his avowed fidelity. The fight is over a seemingly inconsequential matter -- whether to go to the fair.

But in Schwarz's expert hands, the undercurrents in this marriage are about so much more.