By PETE HAMILL

BOSS TWEED: The Rise and Fall of the Corrupt Pol Who Conceived the Soul of Modern New York.
By Kenneth D. Ackerman.
Illustrated. 437 pp. Carroll & Graf Publishers. $27.

IF the gods in their wisdom were to sentence me to 30 days in a prison cell with either Boss Tweed or Al Gore, I would need about 11 seconds to choose my cellmate. Welcome home, Boss.

Condemned for my sins to an ocean cruise, I'd rather share a cabin with Tweed than any evangelist, reformer or improver of public morals, dead or alive. Give me Tweed before any crusader for earthly utopias: religious, Marxist, fascist or neocon. Save me from tinhorn messiahs, and from almost every Republican or Democrat now holding public office. In this era of true believers and invincible mediocrity, give me Tweed.

In his excellent new biography of the Boss, Kenneth D. Ackerman tells again the story of the man who died in 1878 and remains the epitome of big-city corruption. Tweed is a wonderfully vivid subject, a man of gigantic, Rabelaisian hungers. He seems always to have wanted more. More food. More money. More power. Unfortunately, for a long time he got what he wanted.

In the days of his glory (roughly 1863-72), in places like Delmonico's famous restaurant, Tweed gorged on duck, oysters, tenderloin and other culinary delights, and packed more than 300 pounds onto his almost 6-foot frame. He didn't smoke and seldom touched the booze. But as the boss of Tammany Hall, he feasted on a flood of post-Civil War money, stealing with his associates a sum that has been estimated from a low of $1 billion in today's dollars to a high of $4 billion. The ring fittingly began as a ''lunch club'' at City Hall, with Tweed at the head of the table. The others were Peter Sweeny, head of the Department of Parks; Comptroller Richard Connolly; Mayor A. Oakey Hall; a few key judges and legislators and various hungry contractors.

''It's hard not to admire the skill behind Tweed's system, though,'' Ackerman writes. ''The Tweed ring at its height was an engineering marvel, strong and solid, strategically deployed to control key power points: the courts, the legislature, the treasury and the ballot box. Its frauds had a grandeur of scale and an elegance of structure: money-laundering, profit sharing and organization.''

Much of the loot went to maintaining the system itself, in the form of overhead ladled out to corrupt minor players, particularly the upstate Republicans. But a good percentage stuck to the pudgy hands of the leadership. Without shyness or shame, Tweed in 1871 began wearing an immense 10 1/2-carat diamond stickpin, like a badge of success and command. When one of his daughters married that year, the gifts were estimated by one reporter to be worth $14 million in today's dollars. By then Tweed was the third-largest owner of Manhattan real estate, including his own grand mansion on Fifth Avenue and 43rd Street, with its nearby stable full of horses. There was an estate in Greenwich, a race horse and two yachts.

Tweed also reaped a fortune in what one Tammany philosopher later called ''honest graft.'' He was welcomed to the boards of many corporations, handsomely rewarded, and confirmed in his cynicism. He knew that his charm had nothing to do with his good fortune. He controlled City Hall, the governor's mansion in Albany, the district attorney's office, the judiciary and Tammany Hall. Businessmen wanted to know what Tweed knew, and paid handsomely for his company.

His company could be entertaining. Ackerman, also the author of books on President James A. Garfield and the Wall Street crash of 1869, contrasts Tweed with his later enemy, the chilly reformer Samuel J. Tilden, during their 1868 appearances before a congressional panel investigating voter frauds. Tilden was restrained, laconic, icy, his testimony filling only three pages of a thousand-page transcript. Then came the Boss: ''Tweed lit up the room. Big and boisterous, he knew how to lavish the congressmen with humor, look them in the eye, slap shoulders, shake hands, crack a joke, share a confidence, poke fun at his own girth.''

That style was acquired on the streets of New York. Central to the style was Tweed's knowledge of the world as it actually was, not as it should be (in that sense he was a philosophical descendant of Niccolo Machiavelli). He didn't want to change the world. He wanted to know how it worked. Ackerman quotes Tweed in a jailhouse interview, about six months before his death:

''The fact is New York politics were always dishonest -- long before my time. There never was a time you couldn't buy the Board of Aldermen. . . . A politician coming forward takes things as they are.''

Coming forward, young Tweed learned only too well to take things as they are. Curiously, Ackerman pays little attention to the nefarious Tweed predecessor, Fernando Wood, who as mayor (1855-57 and 1859-61) helped create the system of municipal corruption that Tweed and his ring later perfected. When the 29-year-old Tweed was first elected to the Board of Aldermen in 1852, its members were already known as the Forty Thieves.

Ackerman is also sketchy on Tweed's formative years, almost certainly because of a lack of documentation. He tells us what's known: that as a brawny teenager Tweed was a tough street fighter in the Cherry Hill section of the Lower East Side, the son of a chair maker whose own roots went back to Scotland. The boy's alarmed father sent him off to a New Jersey boarding school for a year, where he first studied accounting, a tool that would make possible much of his later life. Tweed became a man who could count and calculate, both the number of Irish immigrants arriving in flight from the 1840's famine -- all potential voters -- or the possible markups of a street paving contract.

We never learn the causes of Tweed's great hungers, and never will. He seems to have written no childhood diaries or letters, stated no vaunting ambitions to his friends. We must be content with the outlines of the early career, from his years as a brawling volunteer fireman to his part in the formation in 1848 of the Americus Engine Company No. 6, better known as the Big Six. The symbol of the Big Six was a snarling Bengal tiger.

Ackerman is superb on the creation of the Tweed system and its expansion from acceptable petty skimming to the glittering fellowship of the ring. In early 1863, with the Civil War raging and war profiteering ever expanding, Tweed became leader of the central committee of Tammany Hall. A few months later, he was elected Grand Sachem, the man at the top. Then came a turning point. When the horrific draft riots exploded on July 13, 1863, most Democrats sympathized with the protesters, if not their violence, but were timid about getting actively involved. President Lincoln's conscription law was boneheaded and unjust, allowing rich kids to buy their way out of the draft for $300 (about $6,000 in today's money) while Tammany's constituents -- most of them poor Irish who could never raise the payoff money -- would be sent off to fight and die for the Union. But during the riots, the new Boss did not flee to a peaceful suburb. He walked the bloody streets, urging calm. Tweed did not inflame violence, he prevented it.

In a way, that display of sensible bravery made him. The establishment nodded in approval. Newspapers applauded. Tweed did not stop with his patrols through the downtown streets. He showed an understanding of one basic principle of the realistic pol: All serious problems might not be solved, but they must be managed. Tweed worked on managing the draft mess, creating a system of exemptions (cops, firemen, militia members) and case-by-case hardship exemptions for heads of impoverished families. The city itself would find substitutes for the exempted draftees, and pay the substitutes $300 bonuses from a special fund financed by the selling of bonds on Wall Street.

''This way,'' Ackerman writes, ''Lincoln's army would get its soldiers and the people would get relief.''

The draft went on, but without riots. When the war was finally over, Tweed for a long time was considered a reformer. As a state senator in Albany, heavy with cash, he fought for and won home rule for New York City. At the same time, it had been scoundrel time in the Republic since the early months of the Civil War. Respectable, well-bred patriots made immense sums selling defective rifles and ammunition to the Union armies, along with rotting food, shoddy uniforms and boots that fell apart in the rain. These habits didn't end at Appomattox. Such men were unlikely to attack Tweed for handing out bags of cash from his hotel in Albany. And when Tweed talked later about the need to take things as they are, he wasn't speaking only of New York. He was talking about America.

At the same time, Tweed's popularity kept growing, for he also did much good, taking care of his base among the mainly Irish poor. This was not a matter of ideology (although Tammany supported the cause of the Fenian rebels in Ireland and the Cuban fighters for independence from Spain). Tammany was populist but not ideological, and Tweed's personal style remained essentially the same: the exercise of power with a conspiratorial wink.

''His aid took many forms,'' Ackerman writes, ''state money for schools and hospitals, lumps of coal at Christmas, and city patronage jobs to put bread on family dinner tables.'' Tweed crossed the barrier between church and state by providing money to the emerging Roman Catholic parochial school system (without any slippery faith-based rhetoric). But there were few protests, except among the anti-Catholic bigots. It was assumed by most others, including those who benefited most, that his generosity was all about votes. As it was. But one thing was certain: Because of Tweed, New York got better, even for the poor.

The story of Tweed's rise and fall is told in a crisp, clear way. Ackerman explains how Tammany was critically wounded by New York's Orange riots -- battles between Irish Catholics and Irish Protestants that left 8 dead in 1870 and 67 dead in 1871. Graft was one thing, disorder another, and memories of the draft riots were still vivid. Now Tweed was under direct attack, the charge led by The New York Times of George Jones and by Thomas Nast, the brilliant cartoonist of Harper's Weekly. Ackerman gives an excellent account of the unfairness of both, but is especially instructive about Nast, who was virulently anti-Catholic. Nast -- who had created the Republican elephant, the Democratic donkey, and the image of Santa Claus -- adopted that Bengal tiger from the Big Six as a symbol for a predatory Tammany. Ackerman is also persuasive about the way Nast invented statements for Tweed that helped bring him down, the most famous being: ''Well, what are you going to do about it?'' Tweed never said it.

But there was another factor in the great fall. Ackerman explains:

''The ring had only one fatal flaw: its humanity. Human beings composed it, governed by greed, vanity and fear. Greed ultimately took control; they stole too much and lost their nerve. Treachery broke the ring more than any outside force.''

The treacherous toppled the Boss, carrying copied accounting records to The Times and forcing action against the conspirators. The ring crumpled swiftly. Connolly and Sweeny fled to Canada and Europe. The elegant Oakey Hall was acquitted twice and sailed off to exile in London. Only Tweed went to jail.

Ackerman tells again the story of Tweed's escape from custody in 1875, to New Jersey, Florida, Cuba and finally Spain, where he was arrested and returned to jail in New York. He would never again be free. Tweed thought he had an agreement with the state attorney general (and indirectly with Tilden, now governor of New York) to confess all, in exchange for freedom. He confessed in 1877, and was double-crossed by the lawmen and pols. Held for nonpayment of a civil judgment of $6.3 million (today more than $125 million), Tweed died at 55 in the Ludlow Street civil jail on April 12, 1878. His own fortune was long gone. His wife and most of his children were gone too.

Surely when the news of his death spread through the city, some of Tweed's constituents must have remembered the time in 1875 when he was taken for imprisonment to Blackwell's Island. He was asked by a jailer to state his religion, and answered ''none.'' Then he was asked his occupation.

''Statesman,'' Boss Tweed answered.

Across the years, I can still imagine the wink, and the cynical smile, and the dark laughter. Welcome to the cell, O lost boss. You can have the bottom bunk.

Pete Hamill is distinguished writer in residence at New York University. His new book is ''Downtown: My Manhattan.''