By Lily King

Atlantic Monthly. 237 pp. $24

One cannot read a novel about an American abroad without thinking of Henry James's coming-of-age novels and, more recently, Diane Johnson's delightful "Le Divorce," a modern improvisation on the Jamesian theme of a naive American coming to Paris and being transformed. Lily King's ambitious first novel, "The Pleasing Hour," is a playful departure from this genre. Rosie, a 19-year-old American who goes to Paris as an au pair, is not exactly one of those innocents. She is running away from a complicated past.

With wry humor, Rosie recounts her year living with the Tivot family on a houseboat in Paris--hardly the conventional setting. Her observations of the daily life of a French family are acute and unsparing. For Rosie, going shopping for the first time with Nicole Tivot, the French mother, is a comedy of errors. Nicole makes her so nervous that she forgets all her French words. Nicole is beautiful, elegant, cool, impatient, judgmental. Rosie, who is large and ungainly, constantly blunders.

Rosie's charges, the three Tivot children, are 9-year-old Guillaume, a mother's pet who wants to be a priest; 12-year-old Lola, who craves her mother's love; and 16-year-old Odile, who, on the verge of her sexual awakening, is drawn more to girls than to her boyfriend. Snubbed by Guillaume and Odile, Rosie is closest to Lola. The portraits of the children in the novel's second part are full of rich stories, one of which recounts a family visit to a priest who advises Guillaume not to waste his life in the priesthood; another satirizes a French dinner party. Unfortunately, Rosie is completely left out of this part, as the narrative shifts from her fresh, wonderful voice to third person.

While cultural and linguistic barriers lead only to miscommunication and humiliation with Nicole, they vanish when Rosie is with Marc, Nicole's husband. Marc, a doctor, is slightly awkward, not handsome, self-conscious, eager to please and, like Rosie, an insomniac. Rosie, who is very lonely, becomes infatuated with him, and during a family holiday trip to Spain a secret, brief romance begins. King has a wonderful ability to get inside her characters. She captures the complex family interactions and silent tensions between Marc and Nicole, and gives a certain weight to the cliched romance between a smitten 19-year-old and a man twice her age who is starved for love.

Rosie's reminiscences of her troubled past could be a separate book. When she was little, she lost her mother and became very close to her older sister, Sarah. Because Sarah could not have children, Rosie, still in high school, got pregnant so that she could give her child to her sister. After the birth, the only way she could cope was to run away to Paris, where, in the Tivots' kitchen, she silently mourns for her baby.

The problem is that we are not persuaded by this story. King tries too hard, piling too many tales on top of each other without developing them fully or tying them together. Another subplot interspersed throughout the novel is Nicole's family history. Her mother, Marcella, marching through a French village after the Liberation with a swastika of tar on her chest as punishment for consorting with a German officer during the war, is a powerful image. But, seeming merely tacked on, this story weighs down the narrative. Marcella's inexplicable disappearance when Nicole was very young is supposed to make us understand Nicole's detachment, her incapacity to receive or give. Nicole, however, remains an icy, somewhat two-dimensional character.

Nevertheless, "The Pleasing Hour," when not burdened by these flashbacks, is delightful. In Spain, a wonderful reversal of roles occurs: The French family, stripped of its language, is totally dependent on Rosie's American ability to adapt like a chameleon and speak her newly acquired Spanish. Ironically, during this trip, just as Rosie and Marc betray her, Nicole begins to trust Rosie. How much Nicole knows about what is happening between her husband and Rosie remains ambiguous. With sensitivity, King traces the shifts of power and the intricate relationships of this triangle. We realize that Rosie and Nicole are much more alike than they seem and are both struggling to come to terms with the past. Our heroine subtly observes that because she loved Marc, he stopped asking so much of Nicole and gave her more room to love him.

At times, the narrative is in danger of collapsing from the weight of the different stories. Yet this remarkably well-written book will please you with its funny and sad tale of cultural differences, love, betrayal and motherhood. Whatever its flaws, this first novel introduces a very talented writer of great promise.

Lelia Ruckenstein, a book reviewer who lives in Hoboken, N.J.