But hardly anybody, outside a small circle of police scholars and New York history buffs, remembers David Durk, an intellectual, suit-and-tie-wearing detective who was Serpico's close friend and fellow songbird. Unlike Serpico, Durk actually testified before the commission appointed by Mayor John Lindsay to investigate police corruption, and his comments capture the conflict at the heart of James Lardner and Thomas Reppetto's gripping narrative history of New York's finest:

"The average cop, [Durk] declared in his opening statement, longs to be honest but is convinced that 'he lives and works in the middle of a corrupt society.' The police department had become 'a home for drug dealers and thieves' in which 'men who could have been good officers, men of decent impulse ... were told in a hundred ways every day, "Go along, forget the law, don't make waves and shut up."' Any anticorruption campaign that failed to fix responsibility outside the department as well as inside -- and in high places as well as low -- would be viewed by cops as a 'swindle,' he said."

"NYPD: A City and Its Police" is a tremendously ambitious book -- arguably too much so -- that seeks to identify repeating patterns and tidal currents in the story of America's biggest and oldest police force. It's also an enthralling chronicle full of colorful heroes and villains, some worthy of Damon Runyon, others closer to the realms of Dashiell Hammett or E.L. Doctorow. We read about the 1836 murder of a prostitute named Helen Jewett, which the authors describe as the O.J. Simpson case of its day, and which led indirectly to the creation of the NYPD nine years later. We learn of the valiant struggle by police officers, mostly Irish themselves, to save black men and women from lynching by Irish mobs during the catastrophic draft riots of 1863. We meet such legends as Sam Battle, the department's first black recruit, who outlasted ingrained racism in his long and distinguished career; Johnny Cordes, the detective who was shot five times during a 1923 arrest -- including twice by a fellow officer -- and still got his man; and Charles Becker, the only NYPD officer ever executed for murder (who may well have been innocent).

Police history, Lardner and Reppetto argue, is "a pendular business, the profession swinging decisively back and forth between scandal and reform" at predictable 20-year intervals. This is uncannily accurate, as they demonstrate; the first major NYPD corruption scandal erupted in 1894, and others followed in 1912, 1930, 1950, 1970 and 1992.

Police behavior, in the authors' view, is governed less by the alternating parade of insiders and reformers who have governed the NYPD than by the "hidden ideas and emotions" that make up the organization's "inner life": "the traditions, the fears, the lore and all the lessons, official and unofficial, spoken and silent, that cops pass along from generation to generation." In this context, Durk's testimony is important not just because it depicted the NYPD in its darkest hour but because it brought to popular awareness the idea that cops live by their own code of survival, sometimes melodramatically dubbed the "blue wall of silence," whose prime directive is to protect themselves from the untrustworthy outside world.

The authors of "NYPD" come neither to praise the department and its rank-and-file officers nor to bury them. Lardner, a veteran journalist who writes for the New Yorker and the Atlantic Monthly, and Reppetto, a former Chicago police commander who has headed the Citizens Crime Commission of New York City for 20 years, pursue a reasoned and guardedly sympathetic middle-ground view of the NYPD's total history. They stress that numerous "acts of decency or heroism" have occurred amid the most corrupt regimes, and that the various high-minded reform crusades have not always benefited the department or the city it's supposed to serve.

Essentially, Lardner and Reppetto believe that the problems that have long bedeviled the NYPD -- principally graft and excessive violence -- go clear back to its ambivalent origins in the mid-19th century. Unlike the police forces of major European cities, New York's department was organized under municipal rather than national control and was relatively decentralized of command structure. This meant that the NYPD and its officers were always subject to the vicissitudes of local politics, and by the 1870s what the authors call "the ethos of the force" was firmly established. Certain kinds of "protected vice," such as the Tammany Hall political machine and the gangsterism associated with it, were to be overlooked, but crime understood to be a threat to the established social and economic order was to be ruthlessly crushed.

Readers who know the recent troubled history of New York policing may be startled to read about a controversial, ethnically charged shooting in which cops killed an unarmed man -- in 1857. (The cop was Anglo, the victim an Irish longshoreman known as Sailor Jack.) Then there was the violent clash between cops and Lower East Side radicals in Tompkins Square Park -- during the railroad strike of 1877. Perhaps more expected, and more sobering, are the excuses for brutality that can be found throughout "NYPD." These range from the legendary mantra of Clubber Williams, an aptly named 19th century street cop, that "there is more law in the end of a policeman's night stick than in a Supreme Court decision" to the disgraceful admonition from 1930s commissioner Lewis Valentine -- ironically, one of the NYPD's great reformers -- to "kick the gorillas around."

Lardner and Reppetto's account of the NYPD's near collapse in the 1970s and the startling successes and red-hot scandals of its recent years is necessarily a little abbreviated. In the feud between Mayor Rudy Giuliani and former commissioner William Bratton, they clearly see Bratton as the hero who reenergized the department, and they also lend some much-needed respect to the unjustly abused legacy of former Mayor David Dinkins and his commissioner, Lee Brown (now mayor of Houston). Even in the wake of the Abner Louima and Amadou Diallo cases, the authors believe that the NYPD faces a historic opportunity, with New York's remarkable drop in crime, to forge a new relationship with the city's people. Unfortunately, the portrait they paint suggests that for all the changes the NYPD has seen, its inner life remains the same.

Maya Angelou reads from "The Heart of a Woman"