This most interesting and entertaining book is, as its subtitle indicates, an "inside" look at the daily workings of an American police force. Its author is a British journalist and novelist who, having previously written "Spike Island: Portrait of a British Police Division," decided to cross the Atlantic and see how the same business is transacted here. He ended up in San Diego, which is hardly a typical American city and which certainly does not have a typical American police force; but he learned a great deal about what it is like to be an American cop, and quite by accident he may also have learned something about what the future holds for law enforcement in this country.

This is because San Diego, under the leadership of an enterprising police chief named Bill Kolender, is following a policy called COP, which "stands for the Community Oriented Policing program, a succession of sweeping changes, largely initiated over the past few years, which is still gathering momentum and could well make the department a legend in its own right some day." As originally conceived a decade ago, the program had two objectives, as described by one of its early leaders: "to get the officers to become very much more knowledgeable about their beats, taking a look at everything from socio-economic data to the networks of leadership and communication within the community -- and, most importantly from our perspective, the crime, the trends, patterns, the victims," and "to come up with new ways of doing business in San Diego."

In a phrase, what San Diego has sought to do is to take John Wayne out of the police department. As one officer says, what the police now practice is "a different kind of macho, more subtle." Cops in San Diego do not seem to be a scintilla less tough, when toughness is needed, than cops in other cities. But they are trained to know the communities in which they serve -- white, Mexican, black -- and to know the ways in which tension can be diffused rather than intensified. Where in many other big-city police forces tactics still tend to be aggressively confrontational, in San Diego they are aggressively conciliatory.

San Diego is also determined to have a police force that represents the community it serves. Under Chief Kolender it has vigorously pursued an equal-employment policy that emphasizes the hiring of women and minorities. For all these persons the path to acceptance -- by colleagues and by the public -- has not been easy, but most of them seem to regard the struggle as worthwhile. And for that matter, hardly any of the white males who traditionally dominate police forces seem to have harbored longstanding grudges against their new fellow officers; most seem to welcome the diversity they bring to the force, and to realize that in certain situations they can be more effective cops.

What is as striking as anything about San Diego is that this city of slightly under 1 million is policed, and policed effectively, by a force of only slightly more than 1,000 uniformed officers; Washington, by contrast, a city of 650,000, has a police force of nearly 4,000. The city's laid-back culture no doubt has something to do with the ability of this small force to cope with it, but one comes away from "Cop World" convinced that the real explanation lies in the admirable organization, morale and efficiency of its force.

This is not to say, though, that in San Diego a policeman's lot is all a happy one. Gang warfare in the Mexican district is unceasing and volatile; the drug traffic contributes its usual share of crime; domestic violence, even among the tanned and blissful of Southern California, is frequent and bloody. As one homicide officer puts it: "Whether it's a report I've read, or a suspect I've interviewed, somehow I feel tainted. I go home and take a shower, go over to a friend's jacuzzi. I want to be cleansed of all this ugliness. That is the job: it's ugly. And I guess you say to yourself after that, 'Okay, it's gone for a while. I don't want to get dirty again -- but, damn it, soap and water will get it off.' "

In the world of the police, even amid quiet there is the pervasive knowledge that "things can still go horrifyingly wrong." Danger is ever present, the threat of violence always looms. Yet good men and women are drawn to this work; they welcome what one calls "the opportunity to help the weak," what another describes as the desire "to go out and be on the good side of something." They do their work with diligence and good humor -- "Cop World" is often a very funny book -- and dedication. James McClure has paid them deserved, and articulate, tribute.