By Muriel Spark

Houghton Mifflin. 192 pp. $18.95

HURLEY REED, an American painter in his fifties, and his "lifetime companion," Chris Donovan, a rich Australian widow in her forties, are having a dinner party at their London home. A charming and contented couple, they do these things well. The menu, for example -- salmon mousse, "pheasant with the trimmings," salad and cheese, creme brulee -- may be a little old-fashioned (their chef would have preferred something more nouvelle) but it is carefully planned, perfectly prepared, perfectly delicious.

The eight dinner guests are also chosen with care. With the exception of Lord Suzy, "an intensive-care case of loquacious boredom" married to a former schoolmate of his daughter's, they are an intelligent and sociable lot. A geographer, Ella, married to an international banker, Ernst. A TV producer named Annabel and her genealogist cousin, Roland. ("Ah, the melancholy gay," said Hurley. "But he's very good at dinner," said Chris. "You can put him next to a tree and he will talk to it.") And a pair of newlyweds: William, a researcher in artificial intelligence who will inherit an Australian fortune when his mother dies, and Margaret, a romantic-looking Scotswoman with long red hair, a relentlessly saccharine disposition and "a melodious voice which made the sentiments she expressed all the more mellifluous."

Hurley and Chris are splendid hosts, but some things are beyond the control of even the best hosts. Newlywed William's mother, Hilda, has been invited to drop by later. "But Hilda Damien will not come in after dinner," we are told early on. "She is dying, now, as they speak." Murdered.

Hurley and Chris's dinner party is the centerpiece of Symposium, Muriel Spark's wholly satisfying new novel. Through flashbacks, Spark fills in the stories of the guests, building, with characteristically intricate plotting, to the death of Hilda, the novel's climax as it is the dinner party's. Margaret, the Scots bride, soon emerges as the novel's central character. From their first meeting, mother-in-law Hilda has been suspicious of Margaret, stubbornly convinced that there is something odd about the oft-told tale of how Margaret and her son first met, in the fruit section of Marks & Spencer's, Oxford Street. "She had spoken first: 'Be careful, those grapefruits look a little bruised.' He was enchanted right away."

And indeed there are a number of odd things about Margaret Murchie of St. Andrews, despite her intense niceness and her refusal to speak ill of anyone. There is, for example, her close relationship with her uncle, Mad Magnus, "the only imaginative factor in the Murchies' family," who is canny but insane and spends most of his time in a mental hospital. Then there is the odd series of unexplained deaths in Margaret's past. Is this Scots "goody-goody type of girl" (as Hilda describes her) really some kind of Angel of Death? A figure out of one of the weird Scots Border ballads she and Magnus like to quote? A witchy temptress proffering bruised grapefruits?

Readers of other Spark novels will know better than to expect any easy answers to such questions. What they will expect -- and get -- is a novel whose sparkling surface, all glancing wit and robust social comedy, parts from time to time to offer glimpses of serious philosophical and theological depths.

Spark's humor can be subtle. It also can be wonderfully broad, as in the sketches of the denizens of a very up-to-date Anglican convent (recalling Spark's 1974 novel, The Abbess of Crewe), where Margaret is briefly a novice. Sister Marrow, an artist, is known as "the four-letter nun" for the vocabulary in which she expresses her artistic temperament. Sister Rooke is a master plumber much in demand in ecclesiastical circles, where the drains are antique. Sister Lorne is a dedicated Marxist who smokes too much. She is also married.

" 'Married? Isn't that against your vows?'

" 'Yes,' said Sister Lorne. 'But he worked on a farm. Ecology comes before vows.' "

On another level of humor is the gentle zaniness of this idle pre-dinner party conversation between Chris and Hurley:

"He was vaguely looking at the mantelpiece. 'I adore the Salvation Army,' he said, with what relevance nobody will ever know.

" 'Nivea cream,' Chris said presently, as she sipped her vodka and tonic, 'is my Proust's madeleine. The only reason I use it. Total recall.'

" 'Do you know,' mused Hurley, 'those champagne growers, the Ferrandi family, one of the cousins was killed by his wife with a blow on the head from a bottle of his own brand of champagne. The French make their bottles very heavy. Especially champagne.'

" 'Helen Suzy and Brian have accepted,' said Chris. 'I wonder how long that marriage will last.' "

The novel's title, Symposium, evokes Plato's dialogue about the varieties of love, and the five couples at the dinner party can be seen as representing various contemporary versions. Ernst the banker and Ella the geographer, for example, are brought closer together by their mutual infatuation with a young American graduate student who is putting himself through school by serving at dinner parties such as this one. Both suspect the other of sleeping with him; both are haunted by the spectre of "the dread disease" that lies in wait for the promiscuous.

Love and marriage also crops up as one topic of dinner-party conversation, prompting Hurley, a Catholic, to a splendidly clever argument justifying divorce for Catholics who marry in the heat of passion on the theory that "erotic love is a madness" and insanity is grounds for annulment under Catholic law.

But the real philosophical dialogue in Symposium is not about love nor is it explicitly argued. Rather, it takes place almost between the lines and concerns the mysteries of evil and suffering, destiny and predestination, guilt and intention.

The theological preoccupations of Spark, a Catholic convert (half-Jewish by birth, she was brought up a nominal Presbyterian in her native Edinburgh), do not easily translate into thematic statements. Hers are obdurate fictions, suggestive rather than dogmatic, teasing the reader into thought. There have been 19 of them thus far, beginning with The Comforters in 1957 and including such miniature masterpieces as Memento Mori, The Prime of Miss Jean Brodie and, most recently, A Far Cry from Kensington. Fans will welcome this worthy new addition. Others are urged to discover for the first time what John Updike has called "the grave fun and lucid strangeness" of Muriel Spark.

Nina King is editor of Book World.