A famous New York novelist can't get anyone to come to dinner on Monday nights because all her friends are at home watching "Brideshead Revisited." In Washington, a high-powered agent who gave a swank cocktail party one Monday was surprised to find all his guests huddled in a bedroom watching "Brideshead Revisited" on TV. In Chicago, a company that manufactures stuffed bears is trying to rush out an Aloysius teddy just like the one seen in "Brideshead Revisited."

All across America, champagne and tears are flowing in honor of this spectacularly captivating recherche du temps perdu. The country is all but overrun with "Brideshead" heads and Marchmainomanes.

Already the highest-rated dramatic series every shown by the Public Broadcasting Service here, "Brideshead Revisited" -- a brilliant, sumptuous, mesmerizing British TV adaptation of the Evelyn Waugh novel -- has become what few would have predicted for it in this country, a comet charted by a sizeable and fanatical cult. For those who made the 11-part film, this is an unlikely and gratifying triumph, and for PBS, with its head all but secured in the Reagan administration's guillotine, it is something of a miracle.

Few involved seem to have expected the program, seen in England in late 1980, to generate quite such heady interest. Little, Brown and Co., publishers of a newly issued paperback version of Waugh's 1945 work, expect now to far exceed the 250,000 copies sold in England when the show played there. A spokesman for the publisher, in Boston, says the book, out of print for four years, has re-emerged "Phoenix-like" as a best seller in a way old books rarely do.

In Washington, bookstores report sales are rousing. "We've sold hundreds and hundreds," says a pleasingly plump clerk at the Book Annex on Dupont Circle. Crown Bookson K Street NW, has sold out three times; the Book Annex on Wisconsin Avenue gets 30 requests per day; a clerk at the Book Annex on 19th Street NW says she's seen "nothing like this" since "Roots"; and the manager at Brentano's, on F Street NW, says the store sold out last week and has reordered four times. At Brentano's bookstores in Chicago, "Brideshead" was the best-selling trade paperback last week.

PBS estimates that 5 million people are watching "Brideshead" on Monday nights; the show has surpassed the previous ratings record-holder for a drama, set last year by "Tinker, Tailor, Soldier, Spy." After the first episode, Chicago's public TV station, WTTW, received 500 calls demanding a repeat, and scheduled one at once.

This may seem awfully odd for a sometimes slow-moving, soft-spoken film about British aristocrats in the '20s and '30s, the story of painter Charles Ryder and his relationship with the Marchmain family -- the enigmatic, dissipated and effete Sebastian, the imperious and abandoned Lady Marchmain, the beautiful and determinedly Catholic Julia, and others. In the first four episodes, already aired (the fifth, and one of the most traumatic for all concerned, will be seen tonight), the friendship of Charles and Sebastian bordered on homosexual romance. They held hands, sunbathed nude together at Brideshead castle, walked arm-in-arm through Venice. One might think such a theme would be off-putting to some viewers, but there is no such sign.

The program is more than popular. It takes over the lives of some of those who watch it. In Washington, a guest arrived at a friend's apartment and announced over the intercom, "Charles and Sebastian here; Aloysius couldn't make it." Aloysius is the teddy bear that Sebastian carries about through the first few episodes. The North American Bear Company in Chicago has made a prototype of Aloysius which New York's Channel 13 will offer as a premium during its next funding drive, and the bear may go into general production. At Washington's WETA-TV, a high-ranking station executive has been spotted carrying a similar teddy into his office.

Herb Schmertz, part-time Medici for Mobil Oil, is repeatedly approached by people thanking him for "Brideshead" and thinking it is part of the Mobil-underwritten "Masterpiece Theater"; in fact, it is part of the Exxon-underwritten "Great Performances." Male students on college campuses are said to be affecting "Sebastian-like lifestyles," and designer Ralph Lauren has reportedly asked Anthony Andrews, who plays Sebastian in the series, to be a model for his new fall line, which will be heavily influenced by the '20s finery in which the "Brideshead" characters all but drown themselves.

On a Madison Avenue bus in New York, passengers listened in as a fat little boy ranted on to his mother about Sebastian's drinking and the threat it posed to the family; when the boy and his mother left the bus, a well-dressed man stood up to say to the child, "And a good day to you, too, Lord Marchmain." A group of middle-aged men in Washington who try to play poker without fail on Mondays have now imposed an unprecedented hiatus during the hour in which "Brideshead" appears.

People congregate in homes and apartments to watch together, and drink champagne, and discuss each episode after it ends. A free-lance writer and vivacious hostess in Santa Monica, Calif., says that before each episode she and her friends "all get on the phone and say, 'It's coming, it's coming.' It's like Halley's Comet. Afterward the phone rings and we start talking about what just happened."

She bought herself a $50 teddy which her 13-year-old son, who also watches each episode, wanted to take with him to school; "he is now dressing close to Oxford," where early episodes take place. "I am prone to be a little emotional, so I'll try to be calm," she says in assessing the series. "This is the best thing I have ever seen, anywhere, ever, period."

The producer of the $9 million film, Derek Granger, says from his home in London that he is indeed surprised at American acceptance of the program but that he was also surprised it was so enthusiastically received in England, especially considering the fact that it is methodically paced (by directors Michael Lindsay-Hogg and 28-year-old Charles Sturridge), very long, and fastidious in its fidelity to the book. And yet in England, restaurant business was "severely down," dress circle seats at theaters were conspicuously empty, and guests for dinner parties were hard to come by -- unless they were billed as "Brideshead" dinner parties in advance -- on Monday nights when "Brideshead" was shown. Granger himself was awakened one night at 3 a.m. by noisy students in the flat below who, it turns out, were having a "Brideshead" party. "I said, 'Oh well, if that's the case, I think I'd better join you.' "

Meanwhile, the British teddy bear population multiplied in epidemic proportions.

Granger thinks the extreme popularity of the film can be directly traced to the appeal of Waugh's book. "It is one of those books -- there are very few of them, actually -- that kind of touch a nerve. These are books which almost everyone find irresistible; they persuade every reader that they're part of his own experience. 'David Copperfield' is such a book -- the identification is so great with that -- and 'Brideshead' is another.

"Waugh is probably one of the finest writers of this century, but his other books tend to be satirical. 'Brideshead' is an unguarded and heartfelt book. People sense that, that 'Brideshead' is true, and that's why they respond in this way."

The book was originally to have been adapted into five episodes, but writer John Mortimer came up with 11. Granger is aware that "Brideshead" takes its own sweet time; he says, "People have to be a bit patient with it, I think, but, amazingly, they are. Sometimes there are long conversations that just don't seem to be going anywhere, yet viewers hang onto them as if they were eavesdropping on real people."

Part of the appeal is visual; "Brideshead" is a magnificent thing to behold. Castle Brideshead in the film is actually Castle Howard, near Yorkshire, owned by George Howard, head of the BBC (though "Brideshead" was produced for England's commercial Granada Television, not the BBC); "He has no title," Granger says, but he is "a very grand aristocrat." In episodes eight and nine, viewers will see scenes played on what appears to be the world's most ravishing deco luxury liner. This ship, "the R.M.S. Constantia," is actually an illusory combination of several different locations: The decks are those of the Queen Elizabeth 2; the dining room that of the Adelphi Hotel in Liverpool; the restaurant is above a shop on Kensington High Street in London; and the cocktail bar is that of London's Park Lane Hotel.

The actual cabins are in fact not actual, but sets built in Manchester on rockers so as to simulate a very lengthy storm at sea that sends the actors tumbling and toppling about.

Absolutely relentless attention to detail is one of the distinctive pleasures of the film. Attempts to recreate the past by American TV shows are almost always paltry and pale -- as with NBC's recent film "The Day the Bubble Burst," which tried to make some tacky old costumes and phonograph records pass for 1929. With "Brideshead," an era is truly evoked, down to the last button on a hunting jacket; as with few television programs of any kind, you can lose yourself in this one.

But it isn't just a showpiece; the acting and characters, far removed from American experience, still seem terribly real and important, and the producers cast the likes of Laurence Olivier to play them. In one sense, Waugh did his adaptors no favors by writing Sebastian, the most fascinating character, virtually out of the book about midway. Tonight's episode is a turning point, the last in which Sebastian is seen at length. In episode six, "Julia," he does not appear at all, though he does obviously continue to figure prominently in the story until its stunning 90-minute conclusion, to be seen on March 29.

The filmmakers did shoot an additional scene in which Sebastian appeared, a flashback narrated by his sister Cordelia (Phoebe Nicholls), but they cut the scene during final editing because it was felt, Granger says, "that it diminished the quality of her remembrance if in fact in had to be illustrated." Nothing has been deleted for the American airings (not even some fleeting rear nudity, nor a passionate lovemaking scene in Episode nine) but a tiny bit was added -- "an extra minute of Olivier in Venice, which we had to cut over here for time."

At the center of the "Brideshead" whirlwind, beyond the fascination with the clothes and sets and the upper-class trappings, there is the melodious sense of time and place the film imparts -- a time when people had places and knew them, when there was such a thing as duty -- and the integrity and beauty of the story itself. It really does have great themes, themes of decay, and compromise, and the yearning for permanence and meaning in life, and the irreversible fact that unifies rich and poor: absolute powerlessness when it comes to altering the past.

In New York, a woman grew nervous recently when she noticed that her husband had marked each Monday through March with the initials "B.H." on his calendar. She feared that perhaps he had taken a mistress. But no -- his only mistress, at the moment anyway, is "Brideshead Revisited."