JUNK FOOD and junk books have a number of things in common. One is that both are perceived in a state of isolation. There is real food, which provides some kind of health or nutritional benefit. And there is junk food, which doesn't. It exists in its own squalid ghetto of instant gratification.

Similarly, there are real books, which have vision, or something to say, or redeeming social value. And there are junk books, which don't. A junk book is not an unusually bad collection of poems, or a wretchedly edited encyclopedia. It is a book designed as trash . . . a bunch of lists, a piece of porn, some squalid rented daydream. All quite apart from literature.

But on closer examination, both kinds of junk turn out to have noble cousins. Junk food, for example, is a machine full of candy bars, or a shelf of little packaged "cakes," most of them injected with some kind of filling. The filling, mostly cocoanut oil and fierce preservatives, is a horrible parody of whipped cream. Dreadful! And yet behind this junk looms the noble chocolate of Tobler, the dessert cart of a great restaurant, the madeleines of Marcel Proust. And one has no need to despise the cream puffs at Les Pointes because Drake's Cakes exist.

Similarly with junk books. They are most commonly romantic novels. Absurdly erotic if for men, ludicrously unrealistic (especially as to the heroes) if for women. Full of exotic backgrounds, poorly imagined. Tinsel! And yet behind this junk rise up a whole range of splendid romances, and even a few actual great works, like Jane Eyre.

The Maker of Heavenly Trousers is not a great work, but it's a splendid romance. It's erotic, exotic and unrealistic -- and it's all of these things with style and dash. Even with substance. It's the sort of book a Harlequin would be if it could.

I'll start with the exotic. The setting could hardly be more so. The book opens in Peking in the last days of the Ch'ing dynasty. That is, around 1908. In the Inner City, far from the foreign quarter, there is a "house" consisting of many courtyards and pavillions. Once it was a Manchu temple called the Shuang Lie Sse. Now it's the private residence of a wealthy foreigner who chooses to live in native style. Its current name is the Home of the Five Virtues. Not because this foreigner is some paragon of Confucian morality, but because his five principal servants all are related, and all have the family name of To. To means virtue. To-tai, or Exalted Virtue, is the major-domo; To-shan, or Mountain of Virtue, does the gardening, and so on. The servants, the house, the historic marble lions out front, the tailor up the street who makes those heavenly trousers, all this is richly exotic. Accurate, too, The book is worth reading simply as the portrait of a marvelous time and place. (I'd give anything to have just one pair of socks darned by Exalted Virtue's wife. Instead of neat patches over the holes, embroidered scarlet bats.)

But it is also worth reading on much lower grounds. Let me turn to the erotic, of which there is considerable.

The central plot of the book concerns the wealthy foreigner (who narrates the story and whose name we never learn) and his interest in a girl called Kuniang. When you first met her, she is 12 years old, and she is playing in one of the courtyards with Little Lu, Exalted Virtue's son. She is not Chinese. Kuniang ("Girl") is simply what the Virtues call her. Her father is Italian, Signor Cante de'Tolomei, of a once-great Sienses family. Her mother, a Scandinavian, is dead. While the mother lived, the de'Tolomeis had a nearby apartment, and were one of the three European families in that whole quarter of Peking.

The narrator -- who is young as well as rich -- gives orphaned Kuniang one of the pavilions to live in, and the Five Virtues raise her. She grows into a beautiful young woman. Naturally she plays less and less with Little Lu (seven years her junior), or with Fedor and Natasha, the two Russian children down the street, and spends more and more time with the narrator. At 16 she begins to take her meals at his table. Finally, when she is 19 and he is 34, passion enters their lives. It does so in a way that girls whose amorous experience is chiefly in parked cars might envy.

The narrator has an almost unrivaled collection of Chinese silks. Among them is a great cloak of rose-colored satin, once owned by an emperor. It was used by palace eunuchs to wrap a chosen concubine (who is otherwise quite naked) and carry her to the imperial bedroom. Kuniang (who always sleeps naked) is thus carried from her pavilion to the narrator's. She enjoys the trip. "I always thought it would be much more fun to be a concubine," she says happily. Later, though she considers such ceremonies a bit silly, she does agree to get married.

Kuniang is too young and innocent to carry the whole weight of the book. She doesn't have to. There is also Elisalex, alias the Princess Dorbon Oirad. (That's a Mongolian title, in case you're wondering, though Elisalex herself is Russian.)

Elisalex turns up in Peking because she has been expelled from Russia following the murder of Rasputin in 1916. She was his mistress, following her marriage to Prince Dorbon. She is 25, nobly born (Fedor's grandfather was a serf of her grandfather's), a woman even more fearless than beautiful. And more reckless even than brave. Much as I'd like to have a pair of socks darned with scarlet bats, I'd like still more to have met Elisalex, and shared her adventures in Mongolia and in the palace of Duke Lan. Even to know her in a book is much.

As to lack of realism, there is some of that, too. Obviously I shan't praise it in the way I have the exoticism and eroticism. Instead I shall quickly note that there are one or two excessive improbabilities, such as the strange birthmark shared by Kuniang and Elisalex and the psychic powers of Prince Dorbon, and pass on to the book's final charm.

Like a contection at Rumpelmayer's, it is made of the fines ingredients. Romances are usually written by people with more imagination than culture. Hence the tinsel effect. But Daniele Vare was a man quite as extraordinary as his characters. Like Elisalex, he came of a great family. His was Venetian. Like the narrator and Kuniang, he knew China from the inside. Signor Vare was first secretary in the Italian embassy in Peking from 1912 to 1920 -- and then came back in 1927 as the ambassador. He went everywhere. Besides his novels, he wrote a biography of the last Ch'ing empress, and dozens of essays on Chinese history. Besides Chinese, Italian, French and German, he spoke English so flawlessly that it was his amusement to compose some of his books in our language. The Maker of Heavenly Trousers is such a one. What I've been describing is the original. It's Italians who read Il Creatore di Celesti Pantaloni who get foisted off with a translation.

There is no redeeming social value whatsoever to the stories of Kuniang and Elisalex. But they form one of the most delightful daydreams you could possibly rent.