As Dr. Paul Farmer administers a spinal tap to a 13-year-old girl at his clinic in Cange, Haiti, the child begins shouting in Creole: “Li fe-m mal, mwen grangou!”

“Can you believe it?” exclaims Farmer. “She’s crying, ‘It hurts, I’m hungry.’ Only in Haiti would a child cry out that she’s hungry during a spinal tap.”

Haiti, with its oppressive poverty, diseases and political chaos, is hard for most Americans to imagine, let alone respond to. In Haiti, 25 percent of the people die before they reach 40; the official unemployment rate is 70 percent; fewer than half of the adults can read. The title of Tracy Kidder’s book refers to a Haitian expression that describes these desperate conditions: as you solve one problem, another problem presents itself. For Farmer too, Haiti’s tribulations never lessen, but neither do they paralyze his zeal and energy. Instead, he is galvanized by his love for the people and his indignation at their suffering.

The danger in reading a book on Haiti by an author who has been called “the master of nonfiction narrative” is that one may experience Haiti’s horrors only as the setting for a good story, with Farmer as its eccentric but brilliant main character. Farmer’s life does seem the stuff of fiction. As Kidder himself asks, “How does one person with great talents come to exert a force on the world? I think in Farmer’s case the answer lies somewhere in the apparent craziness, the sheer impracticality, of half of everything he does.”

Farmer grew up in the U.S., but his was not a traditional childhood. To begin with, not much of it was spent in a house. His father, known as “the Warden,” was an energetic, restless man who frequently uprooted the family for the sake of adventure. The family lived for a while on a bus and a boat, sometimes without appliances and often without running water. When Kidder observed to Paul’s mother, Ginny, that none of the busy Farmer kids were couch potatoes, she replied: “No couch!”

Such experiences apparently developed Farmer’s sense of adventure and gave him the ability to sleep anywhere and eat most anything. “He could sleep in a dentist’s chair,” says Kidder, “and consider it an improvement over other places he had slept.”

While a student at Duke, Farmer became fascinated with Latin America, then with liberation theology, then with Haiti. He met a Belgian activist with Friends of the United Farm Workers and toured migrant labor camps near Duke. When he met Haitians at the camps, Farmer became curious about their political dilemma. In Farmer, curiosity is a galvanizing force. His curiosity turned to indignation, his indignation to action. He developed a plan to go to Haiti, and as part of that plan studied anthropology as well as medicine. He received both his Ph.D. and M.D. in 1990.

Today Farmer is professor of medical anthropology at Harvard Medical School and a specialist at Brigham and Women’s Hospital in Boston. But his practice and his home are in Cange. In this squatter settlement he has combined his skills and passions. His love of the Haitian people is informed by his knowledge of their social situation, and his medical skills allow him to serve the streams of people who come to the clinic.

The line of patients at Cange is endless. When they finally reach “Doktè Paul,” he quickly assesses them for signs of disease, infected wounds, and emaciation.

“Haiti had already redefined poverty for him,” writes Kidder. “Cange redefined it again. An individual might exist in misery this great almost anywhere, but it was hard to imagine an entire community poorer and sicker than this.”

There are some success stories, including the story of “Lazarus,” as Farmer calls him, who arrived on a bed frame carried by relatives, weighing 90 pounds because of tuberculosis. Now, with his TB cured, he weighs 150. (The cure rate for TB doubled when Farmer initiated a program of support services for each patient that includes food, child care and transportation to doctors’ appointments.)

But for each patient healed there are dozens of deaths. Many of the dead are malnourished children, and some of them die from diseases that Westerners thought had been eradicated long ago. Tuberculosis, which has all but vanished from wealthy nations, is a major cause of death. Kidder reports that pharmaceutical companies have nearly abandoned research on TB even though in poor parts of the world 2 million people are dying each year from the disease. In Farmer’s words, “Tuberculosis makes its own preferential option for the poor.”

The battle against TB led Farmer to his other work: he fights to wrest medicine, equipment and funding from First World societies that he sees as complacent and even content with the unfair distribution of resources. He flies around the world soliciting funds for health projects sponsored by Partners in Health (www.pih.org). In the evenings, when most of us are asleep, Farmer is hunched over his laptop, trying to pull funds from every possible source. He wrangles, says Kidder, “not much with Third World myths, like beliefs in sorcery, but usually with First World ones, like expert theories that exaggerated the power poor women had to protect themselves from AIDS.”

One result of Farmer’s work, says Howard Hiatt, former chief of medicine at Beth Israel Hospital in Boston, is that drug-resistant TB is now seen by authorities “as a soluble problem.” To Farmer, this means that Lazarus has put one “mountain” behind him.

Kidder follows Farmer as he treks across Haiti to find a tuberculosis patient, flies to Cuba to examine that country’s care of the poor, to Harvard to secure medical supplies, then to Chicago to give a speech. He is not sure he understands this powerful, charismatic and fanatical personality, but he respects his tenacity and humility in the face of suffering.

As he listens to Farmer give a speech on HIV at Harvard, Kidder has an insight: “I felt as if for that moment I could see a little way into his mind. It seemed like a place of hyperconnectivity . . . I thought that what he wanted was to erase both time and geography, connecting all parts of his life and tying them instrumentally to a world in which he saw intimate, inescapable connections between the gleaming corporate offices of Paris and New York and a legless man lying on the mud floor of a hut in the remotest part of remote Haiti.”