What is the author's tone in Mountains Beyond Mountains by Tracy Kidder?

Mountains Beyond Mountains is a thoroughly compelling book. The book is not verbose and is readily understood by the layman despite its medical content. The characters oscillate between being hopeful, frustrated, angry, and at times pleased, yet the tone of the book is never one of despair. The main character, Dr. Paul Farmer, is dedicated to improving the living conditions of the Haitian peasants. His efforts are at times thwarted or made difficult by politics and funding. Regardless of whatever may be plaguing him, Paul seems continuously optimistic. He forges forward and is always willing to give more, whether that be of himself, his money, or PIH resources. This forward momentum and positive attitude keep the book from being one filled with sorrow, although it is easy to imagine how, if the information were presented differently, it could trigger such a response. Instead, the book informs without chiding the reader for ignorance. It gently requests empathy and suggests action. Paul is quick to acknowledge that not everyone can respond in the way he has, and he doesn't begrudge Americans their wealth. He only asks that one contribute accordingly and make informed decisions. Without seeming accusatory, the book asks the reader all to reexamine one's own thoughts and efforts on behalf of the poor.