Fran Lebowitz could have been a stand-up comic. However, she would prefer not to stand up. If she could write lying down, she probably would, but instead she brings herself to sit at a table and compose, in longhand yet, essays and satirical fables that made her, first, a cult item for the privileged and, now (cue trumpets) A NATIONAL SENSATION!

She is a breath of fresh cold air, a living answer to the smile button, a humorist of Menckenish pique and Parkersque aplomb, a 27-year-old woman gifted with a terminal case of antic urban angst and a sense that the world is mad - at her.

Best of all, Lebowitz is an anachronism as well as a professional malcontent. She loathes most of the fads and fancies of our time. You won't find her romping around on any stupid old tennis court. You won't hear her refer to "the bottom line." You won't catch her watering, misting and talking to her potted plants, because she hates potted plants.

Asked if she might be "sort of a reactionary," Fran Lebowitz takes her umpty-umpth drag on a life-giving Carlton and replies, "Uhhh - not 'sort of.' I don't like the time in which I live, and I don't think I'd be happier in any other."

Her big-selling book of essays, grievances, asides and remonstrations - most first published in Mademoiselle or Andy Warhol's Interview - might have been called "The Joy of Complaining." Instead it was called "Metropolitan Life," no contradiction in terms intended. Lebowitz stands up for the big city and its unnatural existence; if you aren't constantly at odds with something, how do you know you are alive?

"The outdoors," she writes, "is what you must pass through in order to get from your apartment into a taxicab."

In defending the glorified miseries of the city and in throwing a welcome wet blanket over the new self-help, self-obsessed, est-meets-West theology of the Lifestyle Set. Lebowitz not only strikes blows where angels fear to dread, she even brings back the aphorism and the epigram:"In New York, it's not whether you win or lose - it's how you lay the blame."

"Perhaps the least cheering statement ever made on the subject of art is that life imitates it."

"Democracy is an interesting, even laudable notion and there is no question but that when compared to communism, which is too dull, or fascism, which is too exciting, it emerges as the most palatable form of government."

"Food gives real meaning to dining room furniture."

"Generally speaking, it is inhumane to detain a fleeting insight."

Generally speaking, Lebowitz deals with life on this planet in the '70s, if any, but there is also an essay on what things might be like on Mars where, she figures, people are the size of microbes and "the favored mode of transportation is infecting a visitor and then hoping that he goes someplace."

All the world is divided into things Fran Lebowitz is "fond of" and things she is not. She is fond of numbered lists, the telephone, uninterrupted sleep, and french fries. She is not fond of Erica Jong, dry cleaners, large groups of people, large groups of people imbibing amyl nitrate, landlords, headwaiters, the Rockettes, brown rice, newspapers, conceptual artists, desserts served in brandy snifters and wall-to-wall carpeting in bathrooms.

Her "two greatest needs and desires," she writes, are "smoking cigarettes and plotting revenge."

How did Fran Lebowitz get to be prematurely crotchety.

She was born in Morristown, N.J., if that helps, and dropped out of high school. She moved to New York at the age of 18 and took naturally to a life of suffering; she is blind in her right eye, "constantly" has bronchitis (but smokes three packs of cigarettes a day anyway) and is also afflicted with a "prediabetic ailment" which means "I can't drink anything with caffeine or sugar - no coffee, no tea, no liquor, no anything. Nothing." She developed a taste for Perrier water "but now that it's become the new Crown Royal Cola, or whatever, I resent it." 'Overnight' Success

Though she eschews fads, she now risks being a fat fad herself. "Metropolitan Life" is in its fifth printing with 86,000 copies in bookstores, and paperback rights were just sold to Fawcett for a formidable $150,000.

Overnight success took seven years, during which she wrote away in a Greenwich Village apartment she fondly classes "a slum" and which she claims contains only stacks of books and a hotplate.

Madeloiselle was a strange place for her work to appear; if you tell her you've never read Mademoiselle, she replies, "Neither have I." Andy Warhol's Interview, where she still writes, is even stranger; the "Factory" where the magazine is put out isn't your typical office.

"There are always people wandering around with glasses of champagne," Lebowitz says, "and fascist dictators are forever being taken to lunch." One office boy arrives for work in his lover's Rolls-Royce. The readership is small but knowing and Lebowitz was sure she was becoming famous.

"Then I started the publicity tour for this book," she says, "and it was a shock to me how little I'd been read. I'd been publishing this stuff for seven years! But I almost never left New York. It never occured to me that I was unknown. I mean, I didn't think I was a world figure, but I thought I was, you know, fairly recognizable. Turns out I was completely obscure."

This doesn't seem to have depressed her any more than life in general has.

"Besides writing, my only other skill is driving. When I was 20, I was a taxi driver for one summer. An illegal taxi driver, because they caught me cheating on the eye test and I had to borrow a friend's license, which we forged. And then for a while I was a chauffeur for Johnny and Edgar Winter - you know, the albino rock stars. That was a much too colorful job for me and I really didn't enjoy it." L.A.'s the Pits

Lebowitz may seem the prototypical Eastern Urban Wreck, but her book has traveled well. It is a smash, boffo, runaway hit in California, which is ironic because on the list of places that Lebowitz can't stand, Los Angeles is at the tippy-top. Los Angeles is "a large citylike area surrounding the Beverly Hills Hotel," she has written.

"I cannot breathe in that city," she says, very quickly, as if expecting a subway train to roar up and drown her out at any moment. "I think they have worse air than New York. As you fly in, you see this, this ORANGE. In New York, it's gray. I think gray's a more natural color for air than orange, don't you?

"I'm uncomfortable in Los Angeles. Physically uncomfortable. My visits to L.A. have been purely business and it's been purely talking to movie people, and talking to movie people anywhere in the world would not really cheer you up. If you're a writer. It's a place that sends for writers and then is hostile to them. I mean, they MAKE you go there. They send you first-class airplane tickets and put you in fancy hotels - and then try not to give you any money."

Besides, there's all that obscene exhibitionistic fitness out there. They're so darn fit - and not all of them to be tied, either.

"Physical activity doesn't appeal to me," says Lebowitz, from her own cloud of smoke. "If any of my friends did jog, they wouldn't tell me. I mean, I'm sure it's good for you, but I wish people would do it inside so we wouldn't have to see HERDS of people all the time. And I hate the clothes. I can't stand those jogging clothes. I think they're all the worst colors. All the worst fabrics. And the people who most probably benefit from jogging are ones who look the worst in them.

"Now in Los Angeles, people do look healthy, but that's because their skin is burned. I mean, you know, in L.A., people in lung cancer hospitals probably look healthy. You couldn't even tell if you were sick in Los Angeles. It's dangerous probably. In New York you can tell if you're sick because you look paler. You know, someone says, 'You look grayer." In Los Angeles, they're so bronze, who knows?" Trendy Decadence

Try telling Lebowitz that New York is dead as the influence capital and that America's gone L.A. and she looks at you as if you'd just gored her cat. Nor does she realize that she's living in print's twilight and that television has taken over. She detiantly continues to read book after book and long for the days when magazines were magazines and not just part of a vast amorphaus media environment.

"When magazines started using market research to find out who their readers were, that was the death of magazines," she says, "because magazines shouldn't ask people what they want. They should tell people what to do. To ask people what they want to read - what a stupid thing to do! Because they don't want to read at all. What they really find out is that people just want to look at pictures. And maybe not even that. They really just want to lie there.

"And these magazines promote these horrible 'trends." And make them up. Sometimes there aren't even five people doing it, but the writer's just sitting there and has to think one up so he says, 'There's a big fad - people wearing paper gloves." And pretty soon, Bloomingdale's has a paper glove boutique."

Lebowitz may constitute a trend herself, but she continues to tilt with almost every trend that trundles along. For instance, hobnobbing with the Beautiful People has not made her any fonder of trendy types who are stoned All The Time.

"I went to a party at a well-known photographer's house. Every single person at this party except me was really famous and really rich. I mean, really famous. And you could not get into the johns in this house. Because everyone was in there taking smack or taking coke, and I thought, 'There really is no excuse for this.' I mean, it's one thing for some kid in Harlem to RESORT to heroin; it is another thing for a world-famous fashion designer with 1,100 million dollars. WHAT is bothering HIM I can't imagine.

"So anyway, I was really in a snit. First of all, it was terribly boring. It was a very boring party because everyone was on lines to the bathrooms. Why bother to go into the bathroom I can't imagine. I guess they don't want the bartenders to see. Or the waiters. Or they don't want to share. I just hate the whole thing." Thumbs Down

Now, here are some other things Fran Lebowitz hates:

"I hate nostalgia.It's one of the things I really hate. For your personal past, or your childhood or whatever, it's all right, but nostalgia for certain periods of fashions that existed in those periods I think is really horrifying."

"I hated 'Star Wars.' I would almost rather have abdominal surgery than sit through it again. It was like television for little boys. That's what most movies are like."

"I don't like news. I am not interested in the events of the day."

"I don't like small children with careers." Thumps Up

Of course, there are certain things she likes. Or would like. She would like, for instance, to have been 'a madcap heiress." She would like to be very, very rich.

"I think you think better the richer you are," she says, unashamedly, as she says most things. "I think I would write better if I were richer because I wouldn't be so cold all the time, sitting at my desk wearing nine layers of clothes because I have no heat.

"Really, I'm against the idea that writers should be struggling and poor. I think there are other disciplines besides poverty. I don't even think poverty is such a discipline. Look at all the lazy poor people there are!"

This sort of talk may make Fran Lebowitz sound shallow and superficial. You will be pleased to know that she does make commitments. She votes in every single election that is held - "including school board elections," because "the one thing that my parents instilled in me was the feeling that I will have to go back to a ghetto in Russia if I don't vote."

And she couldn't just lie to her parents - tell them she'd voted when she hadn't, because "I am a person who in my entire life I have never told a lie that I was not caught on within 10 minutes. I must have a dishonest face."

And now success comes to Fran Lebowitz, ranter and raver, moralist and crusader against use of the word "lady" except "when preceded by the word 'sales.'" Fame won't ruin her. She has too large and entertaining an assortment of nuroses. Like Woody Allen, who is about her size, she will probably never be quilt-free, worry-free or Truly Free in the unfunny sense of the term. 'I'm Not Snobbish'

Still, she relishes signs of having arrived at long last - like the fan letter from Sidney "Other Side of Midnight" Sheldon, "which I treasure," and a mash note from a 19-year-old sailor aboard ship who threatened to make a T-shirt with her picture on it if she didn't write back.

She wrote back.

There is another book in the works, but that may take awhile, since "it took 2 1/2 years to write this one," and Lebowitz has said that "I think anyone who writes for five minutes straight has to have a break for three or four weeks." She arrived in Washington one recent morning after having stayed up all night, only because that's the only way she can arrive anywhere before noon. She prefers getting up at about 1 p.m. If ever.

"If I had to get up and go to work," she says mournfully, "that would be IT."

Most of the reviews of her book have been gushes of intoxicated praise, except for two from the Time Empire (one in People and one in old Father Time itself) and from papers in Wichita and Baltimore.

"They said I was decadent and a know-it-all and snobby. I'm not snobbish. I think it's elitism: they're not exactly the same thing. Snobbish is - well, um. I guess there's not that much difference," she concedes. "But I'm just expressing my opinion. I don't expect to affect people. I don't think I'm Tom Paine or anything. I don't expect to see people throwing their plants out the window. I just want to take issue with these things.

"All my childhood fantasies," Fran Lebowitz says, "centered around people actually asking my opinions of things instead of saying, 'Shut up and eat your dinner.'"