By Mario Vargas Llosa

Translated from the Spanish

By Helen Lane

Farrar, Straus and Giroux. 149 pp. $18.95

JESSE HELMS wouldn't approve of this little erotic novel by Mario Vargas Llosa. In Praise of the Stepmother would give a fundamentalist fits. The original 1988 Spanish edition triggered sharp reactions among some Catholic readers in the author's native Peru, and could hardly have helped Vargas Llosa's unsuccessful 1990 Peruvian presidential campaign. This playful exploration of polymorphous perversity is, after all, calculated to disturb even liberals, pagans and hard-core voluptuaries.

Suspenseful discomfort is a prime tool for the serious experimentalist and master storyteller Vargas Llosa. Revered for the gravity of such works as The War of the End of the World, and read for the crisp plotting and lingual chemistry of classy psychological thrillers such as Who Killed Palomino Molero? he has long been considered a contender for the Nobel Prize. He has often voiced interest in the erotic genre and this sleek fable fulfills all the requirements of the form and adds an internal thorn.

Vargas Llosa's experiment begins with the hetero-sensual and proceeds through generous voyeurism, fetish and horror. These topics are passionately portrayed without explicit crudity. But this is a circular tour revolving around the manipulative sexual relationship of a pre-pubescent male child with his 40-year-old stepmother. Many will run aground on the premise. Those brazen enough to continue will find themselves enmeshed in a tense, cautionary mystery suspensefully wrought to a nasty climax.

The setting is two lush bedrooms and a bath and the cast is distilled to a potent four. Don Rigoberto, a rich, middle-aged widower in Lima, has recently married a beautiful 40-year-old divorcee, Lucrecia. Surrendering the moral and political ideals of his militant youth in the face of pragmatism, he searches for a miniature utopia in his wife, his collection of erotica and his obsession with personal hygiene. His nightly ablutions are ritual purifications to prepare him for a bedroom universe rapturously lit by his imagination. "Fantasy," he says "gnaws life away, thank God."

Lucrecia is good-hearted and delighted to go along with Don Rigoberto's ornate games, and his insistence on using his big clean ears to listen to her abdominal rumblings, and his immaculate nose to sniff out her most intimate scents. They are deliriously happy and their only worry is whether Don Rigoberto's little son will accept Lucrecia into the family without a fuss.

The child, Alfonso, looks angelic and is a bright scholar with gracious manners who has never caused his father a moment's pain. We never learn Alfonso's age. He may be anywhere between 8 and 13 years old. Though he is described as small and fragile, we quickly find that his intentions toward his stepmother are anything but filial and he is physically equipped to exercise them. The reader and Lucrecia herself, however, are suspended in doubt over which of the two is the corrupter and which the victim.

The maid, Justiniana, is the reluctant messenger and witness for what ensues and is the unknowing participant in one of the fables that punctuate the novel.

Vargas Llosa's inclination to layer tales within tales is well displayed in the largely autobiographical Aunt Julia and the Scriptwriter, which was made into a film released this summer. That story of the 18-year-old writer who romances his 32 year-old aunt parallels Vargas Llosa's own short-lived marriage to his Aunt Julia, and is interspersed with the swift, busy plots of a radio soap opera.

In Praise of the Stepmother uses a similar technique incorporating scenarios inspired by Don Rigoberto's love for erotic paintings and prints. Six full-color plates of famous paintings are included in this slim volume, each the trigger and illustration for a fantasy. The fleshy "Candaules, King of Lydia showing his wife to Prime Minister Gyges," by the 17th-century painter, Jacob Jordaens, is the pretext for Don Rigoberto to perform gorgeous mattress feats with Lucrecia for an imaginary audience. Francis Bacon's eerie "Head" becomes the portrait of Don Rigoberto as a monster of perversion.

When Lucrecia begins to fantasize, with Francois Boucher's "Diana at the Bath", the inspiration is the dangerous young Alfonso. Titian's "Venus with Cupid and Music" may represent the fantasy of Lucrecia or Alfonso himself, and the fierce analysis of the abstract "Road to Mendieta 10" by Fernando de Szyszlo is the child's preternaturally mature perception translated by his adult lover.

These inner stories extrapolate and ornament the ongoing narrative, while repeating the basic questions of the work. The role and forms of fantasy, of happiness and of innocence turn on themselves. Is innocence the sweet facade of amorality? Justiniana describes Alfonso as "like a little angel; he doesn't know good from evil." Is happiness a fantasy game played in secret as Lucrecia suspects, "like those theatrical dramas -- so pleasing to the Greeks, those sentimentalists -- wherein gods and mortals mingle in order to suffer and kill each other." The questions radiate heat. In Praise of the Stepmother is a small, powerful incendiary device.

Katherine Dunn's most recent novel is "Geek Love."