Nina Munk’s new book, “The Idealist,” is about the well-known economist Jeffrey Sachs and his “quest to end poverty,” as the subtitle puts it. I know: That subtitle sounds like classic book-industry hyperbole, but, in this case, it’s not. That really is what Sachs has been trying to do. The question of whether or not he is succeeding is where things get tricky.

The quest began in 2005, when Sachs, who directs the Earth Institute at Columbia University, started an ambitious program called the Millennium Villages Project. He and his team chose a handful of sub-Saharan African villages, where they imposed a series of “interventions” in such areas as agriculture, health and education. The idea was that these villages would show Africa — and the world — how the continent could loosen the grip that extreme poverty had on so many of its people.

From the start, the Millennium Villages Project has been controversial. It has soaked up large sums of money — the original seed money was $120 million — which its critics believe could have been better used on more targeted, less grandiose forms of aid. Because Sachs, for years, refused — on ethical grounds, he said — to rigorously compare the results at his villages with villages that didn’t get the same kind of help, development experts complained that there was no way of knowing if the project was making a difference.

“There is zero scientific evidence that the Millennium Villages Project is meetings its goals,” says Michael Clemens, a senior fellow at the Center for Global Development and a leading Sachs critic. Sachs, for his part, insists that the Millennium Villages Project has been a roaring success, so much so that its interventions are now being imitated — “scaled up” — in nations like Uganda, with full government support.