The night is dark, the hour is late and the worst nightmare of an air traveler is starting to come true. La Guardia Airport is coming up fast. In the coach cabin of the jumbo jet are a few dozen sleepy New Yorkers straggling back from Miami vacations. In first class, the retinue of the Mayor of New York—two aides, two bodyguards and a reporter. Edward I. Koch is forward in the cockpit, watching the landing firsthand.

Suddenly the airport is not rushing up to meet the plane anymore. The plane is shuddering, the engines are screaming and this metal behemoth with trembling passengers has turned its nose to the sky like an F-16 climbing out of a dogfight. Soon the monster is ready for another approach, but now the runway is surrounded by neat little rows of ambulances and fire trucks, lights flashing, standing at attention in serried ranks as the plane comes—thud, thweep, thwack—to a spectacularly uneventful landing and taxis off to the gate with its quivering cargo.

The cockpit door swings open, and out to join the white-knuckled masses bounds the Mayor of New York, his smile wide enough for two ordinary politicians, his face as radiant as a little boy's in the glow of a Christmas tree. "Gee, that was exciting!" he says. His shaken constituents are reminded of the first principle of understanding their Mayor: Ed Koch is not timid.

Nor is he easy to ignore. Koch would be a national figure by virtue of his office alone, like Fiorello La Guardia and John Lindsay before him; but now he has written Mayor, an extraordinary political autobiography that has vaulted to the top of national best-seller lists. Mayor (Simon & Schuster, $17.95) is astonishing on two counts. First, it is written with such candor—or hubris—that it leaves the landscape littered with fallen and wounded. Koch describes in painful detail how he reduced several lesser officials to tears, relates with curious relish the incompetence of some of his subordinates and discusses the perfidy of some still-present colleagues. The book has laid Koch open to charges of pettiness, even cruelty, yet the Mayor doesn't always stoop to attack. He calls Jimmy Carter "mean and vindictive," implies that former White House aide Hamilton Jordan lied to him and even criticizes movies and restaurants he dislikes. (He also squeals on the husband of his longtime political adversary Bella Abzug. Martin Abzug, Koch says, is friendly to him behind his wife's back.)

But what is even more amazing about the book is that its author is a politician still in office and eager to remain there; Koch intends to run for reelection next year, presumably without support from New York Governor Mario Cuomo, former Governor Hugh Carey, City Council President Carol Bellamy, Congressman Charles Rangel and dozens of others he attacks in Mayor. "Koch has committed egocide with this book," says Jack Newfield, the Village Voice columnist who is an old Koch adversary. "This book is going to cause his defeat. He lies about so many important people in politics that they will do their best to defeat him."

"Every one of my friends and advisers said, 'Don't write this book, you'll only create problems for yourself,' " Koch confides one sunny New York morning. He is sitting in his publisher's office, fresh from a triumphant appearance on Today and flashing that broad, almost boyish smile he always employs when he speaks of confounding those who disagree with him—a subject that comes up often with Koch. He has no regrets about his book or its timing. "The average book on government is never read," Koch contends. "Who reads Henry Kissinger's books now that he's out of office? How many people have read President Carter's book? I thought I'd bring readers into my mayoral office, like a fly on the wall, and let them see how decisions are made."

Understandably, perhaps, Koch has shown the public a view of himself that is never less than flattering—and critics charge he has done it at the expense of truth. Carol Bellamy, for instance, strenuously denies Koch's story that he reduced her to weeping after outfoxing her on a budget vote. Former Secretary of State Cyrus Vance says he never told Koch that Carter would "sell out" Israel if he were reelected. Charles Rangel says he never demanded patronage jobs from the Mayor in return for his support. "I have no idea why he wrote it," says Rangel, the dean of New York's black political leaders. "It would take a psychiatrist to say what makes him do the things he does."

Those are strong words—and they ignore the fact that Koch may be New York City's most effective Mayor ever. Six years ago he took a municipality that was on the verge of bankruptcy, with a declining tax base and a failing national reputation, and steered it back to financial health. Koch lobbied Congress for funds and cut back on New York City expenditures. New York during his tenure has met its obligations, has returned to the credit market and has become once more a popular destination for tourists. Koch has no false modesty about his accomplishments. "John Lindsay used to say that New York City was ungovernable," he recalls, referring to his glamorous predecessor whose budget policies, Koch says, nearly destroyed the city's financial credit. "What he meant by that was that he couldn't govern it."

Koch's stewardship has earned him an undeniably popular following. In the last mayoral election three years ago, he won both the Democratic and Republican nominations. But his policies—and his attitudes—have alienated many of the liberals who first elected him. Neither Rangel nor former Congressman Herman Badillo, leader of New York's Puerto Rican community, is on civil terms with the Mayor; they accuse him of insensitivity to minority concerns. "Right now, there isn't a single leader with any credibility in the black community who would go to work for him," Rangel insists. Koch bluntly counterattacks, charging that what minority politicians really want from him is patronage, not service to their communities. "I got 60 percent of the black and Hispanic vote in the last election," Koch says. "How can I do better than that?" Apparently he feels he should try. After he was heavily criticized in recent months for including too few blacks and Hispanics among his senior staff, Koch appointed blacks to run the police and corrections departments and named Puerto Ricans to serve as consumer affairs commissioner and deputy mayor.

It is a grim day at a grim place: a February afternoon at the Berlin Wall as Edward I. Koch, on vacation, makes the pilgrimage that has become mandatory for Western politicians. But not for Koch the sepulchral tone and grave demeanor of the ordinary political visitor. Instead, he spies the border guards, uncorks the grin and lets loose with a wave. "It's me!" he yells at the guard tower. "It's Mayor Koch! I'm here!"

On one level, he is the consummate New Yorker, almost a caricature of the sharp-mouthed cabdriver, the wisecracking shop assistant, the I've-seen-it-all city cop, who are all as beloved of stand-up comedians as they are feared by visitors to the Big Apple. Edward Irving Koch has been Mayor of New York since 1978, and his abrasive self-assurance, his sass under pressure have made him the darling of many of his constituents. In 30 years in politics, Koch has been an insurgent lawyer, has broken Tammany Hall's control of Greenwich Village and has served as a liberal Democratic city councillor (1967-68) and Congressman (1969-77). Those experiences, he claims, have taught him that the popular conception of New Yorkers as cold, arrogant and obnoxious is untrue. "Don't assume that courtesy exists outside of New York City and not in it," he says. "We've changed. There are rude people everywhere." Koch, who volunteered as a civil-rights lawyer in Mississippi in the 1960s, has bitter memories of the sheriffs and prosecutors he encountered there. "Everything a Southerner says comes over nicer because of the slow drawl," he says, his voice rich with irony. "It may be just as vicious, but people assume it's nicer."

If Southerners are offended by his remarks, they have plenty of company. When Koch ran for Governor of New York in 1982, he told one interviewer that the attraction of the suburbs and rural areas eluded him. "Who would want to live there?" he asked querulously. The voters responded in kind; Koch was trounced two to one upstate in the Democratic primary by Mario Cuomo. "I was nuts to run for Governor," he says now as his city's most dedicated pitchman. "Being the Mayor of New York is such a wonderful job. A year ago a reporter said to me that people are leaving London and Paris to come to New York City. I told him, 'They are bored there. They come to New York and experience its diversity, its energy, its cultural institutions, its history, its opportunities.' Everything else pales." And yet there are frequent moments when Koch is accosted by some citizen who tells him, "You should run for President." The mayoral smile broadens, perhaps the pulse quickens. He says he isn't thinking such thoughts, but he is obviously pleased that somebody is.

"He was very depressed for a long time after he lost the gubernatorial primary," says one of Koch's few old antagonists who does not rate an epithet in Mayor. "Now that he has a bestseller, he has something to live for, something to get him into the limelight again." Koch denies he was ever depressed, but the book and its phenomenal success have invigorated him. "They're going to make a movie of my life," he jokes. "I wanted Paul Newman to play me, but he's too old."

A movie of Koch's life would need a screenplay by Paddy Chayefsky with a touch of Woody Allen thrown in. The future Mayor was born in New York in 1924, the son of Polish-Jewish immigrants. His father, a furrier, went bankrupt in the Depression, and the Koch family eked out a meager living in Newark, N.J., where his parents had the hatcheck concession for an uncle's catering hall. In 1941 they moved to Brooklyn. Koch served in the combat infantry in Europe in World War II, went to New York's City College as an undergraduate, attended New York University Law School and finally, in the mid-'50s, came to Greenwich Village and began his public career.

Ed Koch has never married, a point he raises in his book in connection with a singularly distasteful incident—the appearance, during his 1977 campaign against Cuomo, of posters crudely accusing him of homosexuality. He says the Governor condoned the smear campaign (a charge Cuomo firmly denies), though he does not claim Cuomo was actually responsible for it. Koch's most public relationship with a woman was his long-standing friendship with onetime Miss America Bess Myerson, 59, the current N.Y.C. cultural affairs commissioner, though their perceived "romance" seemed more an affair of the press than of the heart. Koch explicitly denies that he is gay and bristles when the subject of his marital status and personal life comes up. "That's an improper question," he snaps. "I don't use my personal life to advance my professional life. If I were a movie actor and I were running with the jet set, it would be perfectly proper to ask, but I don't use my life that way."

Such prickliness is very much a part of the Ed Koch personality. Most of the time he is an amiable man and first-rate company, displaying an agile mind and a sharp wit. But when an uncomfortable subject arises, he does not avoid it, he attacks it, going on the offensive against any slight, real or potential. He has lived by himself all his adult life, and he still goes home alone at night—sometimes to his one-bedroom apartment in Greenwich Village, sometimes to Gracie Mansion, the city's ornate mayoral residence. It is in this self-imposed solitude that the sharp tongue and the cutting wit and the certainties were formed—in the soul of a man who has never made the daily compromises involved in living with others.

Compromise and Koch are not easy bedfellows. His job demands that he daily seek accommodation with people he disagrees with—but he doesn't like it. His book recounts a series of confrontations, and always he comes off the clear victor; he was right, they were wrong. No middle ground.

Koch is not a lonely man. "I have a social life, but I don't talk about it," he says. He is close to both his siblings, a younger sister who directs an adult-education program at New York University and an older brother who is in the wholesale carpet business. He socializes frequently with a small circle of old friends, both male and female, and usually travels abroad with them one week a year. But among his close friends are no politicians; he doesn't court their friendship, and he doesn't miss it. He would change nothing in either his personal or professional lives. "I'm one of those people who's absolutely happy in what I do," he says, smiling broadly. "Most people are not absolutely happy. I am." End of subject, end of conversation. Ed Koch, triumphant grin at the ready, strides off for another day of being Mayor, of taking brickbats and throwing them back.