BOOK REVIEW : A Summer Fling With the Seamy Underside of Victorian England : THE SUMMER OF THE ROYAL VISIT <i> by Isabel Colegate</i> ; Knopf; $20; 219 pages

After introducing himself as a retired schoolmaster who has spent most of his life in the English city of Bath, celebrated for its hot springs, its architecturally elegant crescents and its distinctive, if doughy, Bath buns, the narrator virtually vanishes.

The contemporary prose in which he has given us a glimpse of Bath’s history and geography glides smoothly into a more elaborate Victorian style, transporting us to the summer of 1876, when the Queen paid a brief visit to the city.

Those were the days when Bath flourished as a spa, patronized by the merchants and manufacturers who had prospered so mightily that their livers had suffered. The visitors took the waters, displayed their finery and departed without ever suspecting that the resort they so enjoyed was only the most superficial layer of the town’s life.

Behind the Palladian facades and well away from the gleaming hotels lay another, grubbier Bath, one known only to the permanent population.

One of the best-known citizens is, of course, the curate, Stephen Collingwood. In his mid-40s at the time of the story, Collingwood had been a barrister who had taken holy orders after his wife’s death.

Instead of ministering to the spiritual needs of his own sort, Collingwood had chosen to work with the city’s poorest, settling among them in the least attractive part of town, Haul Down, where his failure to love his parishioners as much as he had intended “filled him with shame and self-reproach.” He’s a complex and sensitive man, by far the most sympathetic character in this increasingly sophisticated novel of manners.

Although Collingwood makes a determined effort to enlighten the slum dwellers of Haul Down, they’re resistant to all his schemes. The district, in fact, seems inhabited entirely by clones of Eliza Doolittle’s boozy father, and Collingwood finds himself sadly underemployed.

Rejected by his skeleton congregation, he is inevitably drawn to his natural habitat, where he falls in love with a charming and winsome married woman, as faithful as she is adorable. Their admirably restrained behavior makes the excesses of the less highly principled characters seem all the more squalid.

The author has assembled a remarkably assorted cast, representing the entire gamut of Victorian moral attitudes. In a city as compact as Bath, the permanent residents inevitably cross each other’s paths, and soon the characters are involved in the most elaborate gavotte; saints and sinners changing partners as if on a dance floor.

Just as Collingwood stands for virtue, Caspar Freeling represents vice, though the full extent of his viciousness is withheld until the last quarter of the novel.

For most of the book, we’re encouraged to believe that Freeling is nothing worse than a dilettante, dabbling in the study of ancient religions while ingratiating himself with the respectable citizens of Bath.

They include the frail poet, Peter Tilsey, supporting himself as a newspaper reporter despite his deteriorating health, and the exotic Madame Sophia, who presents herself as a Russian exile, dazzling Bath society with her supernatural powers.

In addition to these star turns, Colegate provides a Victorian microcosm in which virtually every social and cultural stratum is portrayed in action. These traits are so silkily incorporated into the characters that “The Summer of the Royal Visit” never seems to be a didactic novel until the last page is turned. At that point, the reader realizes with some surprise that he’s had a short but intensive course in the seamier side of Victorian England, cleverly disguised as a romance.

Next: Carolyn See reviews “A Solitary Grief” by Bernice Rubens (Sinclair-Stevenson/Trafalgar Square).