The storyteller’s art is all about details – how to frame a story, which particulars to highlight or omit. Each of these choices will shape the narrative, its contours and tone. In the nonfiction realm, few authors are as seasoned as Pulitzer Prize-winner Tracy Kidder, whose latest book is a model of storytelling. “Rough Sleepers” chronicles the pioneering work of Jim O’Connell, a physician who tailored medical care for Boston’s homeless citizens.

As O’Connell quickly realized, practicing medicine with so-called rough sleepers – the British term for those who live on the streets – ran counter to any model he learned at Harvard Medical School. There are no efficiencies or quick fixes, no brief patient visits that yield lasting results. Working with this population relies on time and trust, and requires a “system of friends,” O’Connell’s shorthand for the teamwork that’s involved. Crucially, he discovered that his medical degree was often less pertinent than the bartending skills that paid his way through med school. Indeed tending bar made him a better listener.

Boston Health Care for the Homeless Program opened its doors in 1985, with O’Connell at the helm. It was a one-year post that begat a career. Dr. Jim, as he’s called, was especially drawn to working with rough sleepers, who make up only a sliver of the homeless population. He loved riding with the program’s Street Team three nights a week, and Kidder often joined along, as the van made its rounds through downtown Boston. There O’Connell dispensed hot cocoa, socks and blankets to the city’s rough sleepers — enticements for them to show up for his weekly clinic at Mass General Hospital.

“How do you treat HIV in a person who has no place to live? How do you treat diabetes in patients who can’t even find their next meals?” Kidder asks. “At medical school, questions like that hadn’t come up. (Jim) was discovering the role of the homelessness doctor.”

As the book unfolds, we meet some of the regulars that Dr. Jim treated. Among them is Joanne Guarino, who was homeless on and off for 30 years. She’s one of the success stories. Now a member of the program’s board, she colorfully recounts her story each year to new students at Harvard Medical School.

Then there’s Tony Columbo, a product of Boston’s North End, the city’s old Italian neighborhood. One of seven children, Tony dropped out of school at 16. He slit tires and blew up cars, burned restaurants down for insurance money. A victim of sexual abuse, Tony spent 18 years in prison for attempted rape.

Still, Tony became one of Dr. Jim’s “pantheon of vivid and mysterious patients from years past,” Kidder writes. Lean and muscular, with a powerful handshake, Tony had the unmistakable big personality of a leader, who knew and protected everyone on the streets. He was, in equal parts, enforcer, counsellor and social director. Over time, he became Dr. Jim’s eyes and ears on the front lines.

Like so many of his confederates, though, Tony was in and out of the hospital and respite programs, often leaving AMA – against medical advice. Alcohol and cocaine were among his addictions; hepatitis and bipolar disorder, among his ailments. As Kidder describes it, the revolving door of Tony’s street life, like that of so many in the program, was a dizzying, unrelenting cycle of illness and recovery. One might well feel a case of whiplash and exhaustion just reading about it.

Which begs the question of how Dr. Jim and his team have stayed the course for nearly four decades, building the program into a $50 million medical alliance that employs 400, and serves some 11,000 homeless people a year.

“Housing wasn’t just complicated,” Kidder says. “(Jim) found that if he mused too long about the problem, on the forces ranged against great progress and the disagreements among allies, he grew hungry for his system of friends – the clinic, his colleagues, his patients. ‘I don’t get despairing,’ he told me. ‘But it’s much easier to just go take care of people.’ ”

Kidder threads this needle masterfully, weaving among the tangle of bureaucratic rules that keep homeless people unhoused and the feet-on-the-ground, one-to-one ministry that is Dr. Jim’s calling.

“We just have to enjoy the good days and accept the bad days,” O’Connell says. “It’s sort of the theme of our work. Sisyphus. If you don’t enjoy rolling the rock up the hill, this is not the job for you.”

For Kidder, who lives in Maine part-time, this book was a five-year labor of love, a work of deep embedded research. The payoff is a book that celebrates the great good that one man and his program have done in the face of grueling, unimaginable odds. Kidder has humanized a sprawling, thorny subject by focusing on people, not policy. Nor does it hurt to have the likes of Jim O’Connell, a certified mensch, at the heart of the story.

Joan Silverman writes op-eds, essays and book reviews. Her work has appeared in numerous publications including The Christian Science Monitor, Chicago Tribune and Dallas Morning News. She is the author of “Someday This Will Fit,” a collection of linked essays.