The gradually more insistent incursions of the second world war are deftly brought to bear on Lavinia's heady affair. A sense of gathering tragedy in both the wider world of history and the smaller one of love provide the story with a powerful forward thrust. Yet the greatest pleasures of this novel are single sentences, which evidence a fluidity and grace that is rare in contemporary fiction. Lavinia despairs of clumsy language: "It is one thing to be merely prosaic, but to use words in a way that perverted their potential or denigrated their power was something that violated Lavinia's aesthetic principles."

The hand of Lavinia's betrothed "fluttered involuntarily as if it were the only part of him sensitive enough to register emotion or disobedient enough to display it." During Lavinia's engagement, "her views were solicited even by men who previously would have let her erudition and wit go unacknowledged rather than risk having its appreciation misconstrued." For the two lovers, war "intensified the sense of abandon with which they met and the sense of abandonment after they parted." Moreover, eloquence is paired with incisive content: "It seemed particularly naive to believe that the object of a great love must necessarily be worthy of it."

"Twilight" is made for those grumpy fuddy-duddies amongst us eternally griping, "Why don't they write them that way anymore?" Apparently, they do.

Mosby should get a prize for nuance with the way she beautifully evokes both the twilight atmosphere of an illicit romance and a world fast disappearing.

Raised by an indifferent mother and an unyielding father, New York debutante Lavinia Gibbs is not quite beautiful enough and far too clever to dazzle the rarified social circle in which she travels - nor does she want to settle into a mind-numbing marital routine in order to escape the stigma of spinsterhood.

When a thirty-something Lavinia has the temerity to break off her better-late-than-never engagement to a suitably stuffy member of the upper crust, she willingly shoulders the ill will of her parents and siblings, fleeing to pre–World War II Paris with a small monthly allowance and a large dollop of hope.

Diminished by both her family and society, she takes her first shaky steps toward freedom and fulfillment by embarking upon a steamy affair with a married Frenchman. However, when the Germans march into Paris, she discovers that passion and love exact a heavy price that must be paid in full.

With a surprise ending reminiscent of Edith Wharton's Ethan Frome, this poignant character study traces the precarious evolution of a heart and a mind."

   Katherine Mosby prefaces her new novel, "Twilight," with a quote from Jean-Paul Sartre: "Freedom is what you do with what's been done to you."

   On the face of it, freedom would not seem to be a central issue in the life of Mosby's heroine, Lavinia Gibbs, a daughter of New York's ruling class, raised to marry well, bear children, entertain all the right people and attend all the right parties. But Lavinia's first taste of freedom -- a steamy stolen kiss and furtive caress from a charming rogue behind a potted plant at a cotillion -- derails her dutiful march toward her prescribed fate and onto the rocky path charted by her own choices.

   Mosby has set her book in the years leading up to the Second World War -- though a reader could be forgiven, particularly in the novel's early pages, for conjuring images of Edith Wharton's Gilded Age -- a time of seismic changes all around: Brave choices often came at a steep price, and cowardly ones at an even steeper one.

   Lavinia makes a few of each. Engaged to marry a suitable young man whom she admires but, alas, does not truly love, she meets up with a brazen former suffragist who challenges her to follow her heart. Naturally, Lavinia's heart tells her to ditch the young man, bringing shame on herself and her family and necessitating a move from New York to Paris, away from everyone and everything she has ever known.

   There, in the City of Light, Lavinia finds freedom. Freedom to venture out of her social class. Freedom to smoke in public. Freedom to carry on affairs with men just for the fun of it. Freedom to set up house for herself, on her own terms, to adopt a pet, to get a job. Freedom to fall in love with an altogether unsuitable sort of man and to discover her own beauty, to tap into her own desire and, ultimately, to uncover her own capacity for compassion and humanity.

   We're held captive by every bit of it. Mosby sweeps us into Lavinia's world and holds us there, moving the action along at a brisk clip, shuttling us inexorably toward Lavinia's deeper understanding of herself and the unsettled, unsettling circumstances that surround her, but pausing here to bask in the scent of a cologne or a cup of coffee or the thrill of an accidental touch of skin, and there to linger on the language of a seduction in its twilight. Indeed, Mosby fills entire pages with missives sent between Lavinia and her paramour, love letters in which they report the quotidian details of their lives and increasingly bare their souls to each other, and in which they flirt and fight and make up.

   "Dearest Gaston," Lavinia writes, in one typical example. "It has just started to snow. I can deny you nothing when it snows. It's so beautiful right now I can almost forget all the ways I will regret this later. I accept your invitation [to meet] but you must promise to never ever correct my French grammar again, especially irregular verbs. Especially when I am naked. Stick to pronunciation if you feel compelled to improve the way I use your language. I'm sorry I threw the gold bangle bracelets at you but don't ever call me a noisy woman again because I'm not. I hate this fighting."

   Sure, Mosby employs an old-fashioned device to tell the story of an old-fashioned sort of romance, but "Twilight" never slips into the tired terrain of the cliche. The lovely language and lively characters keep it fresh. One feels, instead, as if one has been given a new classic to enjoy -- albeit a particularly light and almost startlingly simple one (as Lavinia's acquaintances are carted off to their fate by the occupying Nazi forces, Lavinia barely notices, so consumed is she with the minutiae of love) -- with a glistening modern-day veneer of feminism baked onto its surface.

   Lavinia's story is one woman's tale of awakening, and of learning to care not just about and for herself but to care for others as well. Her journey, set in motion by a woman and propelled by a series of men, is completed, unexpectedly, with the help of another woman, whose companionship and love she discovers when she is bereft of all else. After all, as a famous person who was not Jean-Paul Sartre once said, "Freedom's just another word for nothing left to lose."

Born at the turn of the century, she has disgraced her family by spurning her boring fiancé. Lavinia settles into a quiet middle-aged life of small activities until her restlessness propels her to begin working for Gaston Lesseur, a banker who is readying the apartment of his late father-in-law for sale.

Gaston, an occasional lothario who is fond of his wife and will never leave her, is taken with Lavinia's American independence.

What begins as an employer/employee relationship conducted mostly through correspondence explodes into a passionate affaire de coeur.

With the drumbeat of war sounding evermore in the background, Mosby takes her readers through the heady details of a new romance that blinds lovers to the costs of adultery.

The tensions of war and the strain of an illicit union collide in the author's now signature twist of fate, resulting in an ending both startling and fitting.

Mosby first introduced Lavinia in The Season of Lillian Dawes. Readers entranced with the beautiful precision of Twilight will demand this earlier title.

Highly recommended."

She is in fact a complex character at odds with the social customs of her time. The appeal of Mosby's novel depends far less on its storyline than on its smooth-flowing subtle prose that gently enchants the reader with observant commentary and lyrical turns of phrase.

"It would be misleading to say that the course of Lavinia's life was diverted by a kiss," the author begins, "or that a chance remark would change the continent on which she lived, although both things were true." Because her fiance's kiss repulses her, because Paris before World War II is a place an unmarried woman can live as freely as she chooses and because her broken engagement brings scandal on her family, Lavinia relocates to Europe with an independent income and no emotional ties.

Her first liaison is with a man on his way to fight in the Spanish Civil War. At this point, some readers may think the novel will present a series of erotic adventures. Those readers will be disappointed. Mosby's fiction is about a sentimental, not sexual, education.When Lavinia loses her heart to a wealthy man married to a French aristocrat, she discovers the real meaning of love.

Parts of the novel stand out for their depiction of the conflict between social custom and personal feeling. In one, Lavinia's correspondence with Gaston reveals their affair is based on a shared love of language as well as mutual attraction.

Fans of Mosby's "The Season of Lillian Dawes" may conclude that the author has not lived up to her reputation, but readers who appreciate poetic language and psychologically complex portraits of women in settings reminiscent of Edith Wharton or E.M. Forster will savor this portrait of a not-so-young lady who defies the conventions of her time only to find herself caught up in history.