WHEN FRANCOISE SAGAN, the celebrated French novelist, was hospitalized in the late 1970s for what turned out to be merely an intestinal obstruction, few of her readers probably thought her writing or her attitudes towards life and love would be changed much. The fast living author of Bonjour Tristesse, a tremendous bestseller in 1954 when she was only 18, had, for 25 years, writer, only of the rich and the worldly suffering through disillusionment and failed love.

Yet the ordeal of facing possible death (when she was hospitalized. Sagan believed she had cancer) seems to have changed her writing greatly-indeed far more than a near fatal car accident which put her in a coma for three days when she was 20. The Painted Lady, just translated into English, bears little resemblance in form or outlook to her earlier 12 novels.

Some 10 wealthy passengers have each paid $15,000 for a 10-day cruise through the Mediterranean aboard the Narcissus. The luxurious ship provides both musical and gastronomical delights. A virtuoso pianist and a renowned diva perform nightly to passengers who dine on gourmet food and turn adulterous in the moonlight. Indeed, affair after affair develops among the passengers.

THE MOST STRIKING relationship and the one which forms the core of the novel is the one between Julien, a card player and roguish art dealer who hopes to sell a forged painting on the cruise, and Clarisse, a sullen and withdrawn heiress who is married to Eric, a radical publisher who takes her for granted and treats her like a child.

Clarisse is "the painted lady" of the novel, a women so filled with self-doubt that when she coats herself in make-up she appears "grotesquely thick and gleaming," hiding herself behind a veneer of cosmetics. Yet Clarisse emerges as the heroine of the novel as something, perhaps a mutual pity, draws her and Julien together. It begins at the dinner table when "as he leaned to give her a light, and her shimmering fawncolored hair momentarily entered his field of vision, bringing with it a whiff of perfume, Julien discovered with surprise that he desire her."

As her self-respect returns, Clarisse's need to hide herself vanishes, and in a striking scene Julien sees her true beauty; "Just then the beacon from the lighthouse crossed her face and Julien was left petrified. Her make-up had given way under the tears and Kleenex and like the ramparts of a city it had crumbled and seeped away."

Meanwhile, Clarisse's husband is enduring an emotionless affair with a vapid starlet, while the sensual diva leads on a young gigolo who ultimately kills himself over his love for her. The subplots enthrall, but all fade away as Clarisse's and Julien's love reaches its promising resolution.

SAGAN'S STYLE in The Painted Lady differs sharply from her previous works. Gone is the simple narrative. Here she writes in a much richer descriptive style. One finds few of the short, direct remarks which carried her first books, such as the narrator's comment in Bonjour Tristesse that." They were both smiling happily, and I was very much impressed, for happiness has always seemed to me a great achievement." Instead, Sagan indulges in profuse description, as when Clarisse rains kisses on Julien's face; "Julien felt his face open up, become a fertile and blessed land, a gentle and handsome face washed of everything, precious and perishable, a face forever cherished."

In fact, Sagan's whole outlook on life and love seems to have changed. Love in her previous novels appeared as perfect yet infinitely elusive, a cure-all which could not be temporary. Now, now-ever, love does triumph, at least for two of the characters, and lasting happiness appears attainable. This is refreshing, yet somehow forced. Sagan has been criticized in the past for taking on too pessimistic a view of life and love, and now seems too eager to refute the charge.

Her first books were brief works (usually under 200 pages) with only a few characters, and the simplicity and innocence of the narrators were striking. The Painted Lady is far longer and the complex plot keeps one confused about who is romancing whom. Which is not to say that this new novel fails; just that one can't help feeling that through the years, some exuberance even in pessimism was lost Francoise Sagan's new novel reflects this loss and, entertaining as it is, is the weaker for it.