Fiona Sweeney wants to do something that matters, and she chooses to make her mark in the arid bush of northeastern Kenya. By helping to start a traveling library, she hopes to bring the words of Homer, Hemingway, and Dr. Seuss to far-flung tiny communities where people live daily with drought, hunger, and disease. Her intentions are honorable, and her rules are firm: due to the limited number of donated books, if any one of them is not returned, the bookmobile will not return.

But, encumbered by her Western values, Fi does not understand the people she seeks to help. And in the...