Lone Ranger : TROUBLEMAKER: One Man’s Crusade Against China’s Cruelty.<i> By Harry Wu with George Vecsey (Times Books: $25, 328 pp.)</i>

A sensible man who had survived 19 years in the Chinese gulag and then wangled an exit visa to the United States might be content to settle down into middle-class domesticity and keep his distance from Beijing. But Harry Wu is anything but sensible.

Part crusader, part crank, part show-off, Wu has four times tempted fate by returning to China and documenting with hidden cameras that nether world of labor camps, prison farms, mines and factories where the Chinese lock up their worst troublemakers. The Chinese call this penal system laogai, literally “reform through labor.” The theory behind it is that working in these state-run enterprises reforms the prisoners, whether they are petty criminals or political dissidents, while boosting the gross national product.

Wu’s goal, as set out in this, his third book since immigrating to the United States in 1985, is to make the term laogai “known all over the world in the same way that ‘gulag’ became synonymous with the horrors of Stalin’s prison system.” The laogai, he argues, is quite simply “the biggest concentration camp system in human history.”

Wu has not yet forced “laogai” into English-language dictionaries, but he has scored other successes. Through congressional testimony and television documentaries produced from his surreptitious videotapes, Wu has alerted Americans to the flow of prison-made consumer goods--toys, clothes, electronics--from the laogai to foreign markets. A daring muckraker in the best American tradition, Wu has also exposed the burgeoning trade, throughout Asia, in kidneys, corneas and other organs forcibly removed from Chinese prisoners on the eve of their executions.

Wu knows the laogai system first-hand, having been shipped off to his first camp as a college student. His offense: criticizing the Soviet invasion of Hungary. That initial three-year sentence stretched into 19 years, as Wu was shuttled from camp to camp, without access to judicial appeal. The son of a wealthy Shanghai banker, Wu learned survival skills from hardened prisoners with names like Big Mouth Xing. When you’re starving, he was taught, search for rat holes in the walls of your cell, because rodents neatly put away stores of clean food for hard times.

The tales of Wu’s wanderings, Candide-like, through the laogai were told vividly in his 1994 book, “Bitter Winds: A Memoir of My Years in China’s Gulag,” still the most thorough and compelling account, in any language, of life inside China’s forced-labor system.

“Troublemaker,” the current book, suffers a bit by comparison. We hear, in passing, some of the same yarns about the laogai, but they have a hurried and twice-told feel about them. As an American citizen revisiting China in the 1990s, he managed to talk his way back into the prison where he had watched friends starve to death and the coal mine where his back was crushed by runaway coal cars. But these stories barely skim the surface, reading like alumni bulletin accounts of class reunions: Wu even dined, amiably, with an ex-guard.

The problem, I suspect, is not simply that he had a better collaborator, Sinologist Carolyn Wakeman, on the earlier book, but that his story then seemed fresh. “Troublemaker” focuses on his latest attempt to enter China at a remote crossing on its border with Kazakhstan and his subsequent two-month detention at a government guest house.

His June 1995 arrest blossomed into an international incident, put the governments of China and the United States at loggerheads and nearly scuttled First Lady Hillary Rodham Clinton’s participation in the United Nations women’s conference in Beijing.

Despite the headlines, it’s difficult for Wu and his current collaborator, the able New York Times reporter George Vecsey, to disguise the humdrum facts of his latest detention. He had no reason to search hungrily for rat holes this time: The kitchen sent up three ample meals a day. And although the herbal medicine his captors offered for his back pain brought on severe nosebleeds, he did not suffer much physically: There were no round-the-clock interrogations, no beatings, nothing much even in the way of psychological abuse, unless you count the guards’ monitoring of his bathroom habits. Mostly, the Chinese seemed bewildered about how to get rid of their unwelcome guest and end the diplomatic impasse.

A shrewd U.S. diplomat, Daniel W. Piccuta, saved the day by decoding the signals Wu was receiving from his guards. They had commended Wu for his “cooperative attitude,” and Piccuta realized that meant the Chinese were willing to compromise, if only Wu and the Americans could concoct a face-saving way out for both sides. So he confessed to several offenses, including sneaking his cameras into China, was put through a show trial and deported.

Wu is not deeply introspective, but he recognizes that his eagerness to confess might confuse some American readers, since it is clear he broke no laws by trying to reenter China with a valid U.S. passport. “Americans like to think everybody is bound by the same rules, to tell the truth at all times, to mean what you say and say what you mean,” he explains. “But I was dealing with people who could not be trusted, so I had to match them.”

“I was lying,” he also says of his confession. “They knew I was lying. I knew they knew. But they had no problem making a deal with somebody they knew was lying to them. That is how their system works. Everybody understands.”

Wu learned that cheerful brand of amorality in the laogai, and it undoubtedly helped him survive, in his earlier imprisonment, deprivations and horrors that Westerners can scarcely imagine. But, admirable as he is, unfailingly courageous and inventive, Wu may not be a completely credible proponent for his cause.

His estimates of the laogai’s current population--somewhere between 6 million and 8 million--are thought to be exaggerated by many human rights activists. His tendency to misrepresent himself and to steal documents from the desks of Chinese bureaucrats violate every code of journalistic ethics. And that last trip to China, the one that landed him in detention for two months, was considered pure showboating by U.S. diplomats and other critics; he had plenty of confederates who could have gathered the information he was seeking--about World Bank subsidies of Xinjiang labor camps--without jeopardizing U.S.-China relations.

As “Troublemaker” demonstrates, Wu never much worried about geopolitical matters, or even what might be best for the Chinese masses, all 1.2 billion of them. A zealot rather than a strategist, Wu argues in the book’s concluding pages that the United States should punish China for its human rights transgressions by suspending its most-favored-nation trade status for a year. That would send tariffs soaring, slash Chinese exports--and just possibly end the careers of the pro-American members of the Chinese Politburo. Four U.S. presidents, Republicans and Democrats alike, have rejected that notion, fearful of the consequences of isolating Beijing. Harry Wu styles himself a man of the world, nobody’s fool, but on the subject of how to change China, he’s about as enlightened and far-thinking as John Foster Dulles.