Kim played an important role in the foundation of PIH and I learned the most about him through Mountains Beyond Mountains, which captures the mission of Paul Farmer in creating the Partners in Health organization. PIH was a bit radical in its inception by clearly stating a preferential option for the poor in health care, but since its exponential growth and publicity, this notion isn't so controversial. No doubt due to the success of both Farmer and Kim.
I think I read Mountains Beyond Mountains six or seven years ago (again CBT hat tip), but it is still at the top of my list of best books of all time. Despite my economist training and mathematical background, the drive of Farmer, a doctor and anthropologist, is actually what motivated me to study international development. If you haven't read MBM (and I haven't already hassled you about it), get off the computer and go to the library. Right. Now.
And just to be clear, its a good thing Obama didn't nominate Bill Easterly. As a clever and harsh critic of the World Bank, he wasn't quite up for the job.