Author Tracy Kidder met Dr. Paul Farmer in 1994 when he was reporting in Haiti, and the two kept in touch for the next several years. Kidder ran into Farmer at Brigham and Women's Hospital in Boston, where Farmer was treating a patient strugging with tuberculosis. Kidder read and admired Farmer's book Infections and Inequalities, and Farmer invited him to come to Haiti to see his real work.

Farmer's ongoing legacy in Haiti is Zanmi Lasante, a hospital and health center in Cange, one of the most neglected regions of the country. Since college, 44-year-old Farmer has traveled back and forth between his work in the United States and his passion reforming public health in Haiti.

Farmer grew up in Florida in a poor family. He attended Duke on a scholarship, where he studied anthropology. After graduation, Farmer spent a year working in Haiti before studying at Harvard Medical School. During his time at Harvard, Farmer traveled extensively between Boston and Cange. He co-founded Zanmi Lasante in 1983, then continued his crusade against infectious diseases across the globe.

To support his work, Farmer founded Partners in Health in 1987. PIH is headed by Ophelia Dahl, and primarily financed by a Boston construction firm owner, Tom White. While in Haiti, Farmer was able to revolutionize the treatment of diseases like tuberculosis with a combination of drug treatments and improvements to public health. With the support of PIH, Farmer took the treatment to a slum in Peru and a prison in Siberia, bringing first-world health care to people who otherwise would never have access.

Farmer used the research arm of PIH, the Institute for Health and Social Justice, to work towards lowering the prices for the drugs needed to treat tuberculosis. He also helped change the World Health Organization's protocols for treating these diseases.

In Mountains Beyond Mountains, Kidder profiles Farmer and his upbringing, and shadows Farmer's work across the globe. He portrays Farmer as an enthusiastic and inspired doctor who quickly earns the trust and admiration of those who work with him. To accomplish his goals, Farmer sleeps little, works almost constantly, and only sees his family (his wife and little girl) a few times a year. Through the book, Kidder shows just how much of an impact one person can have in changing the world.