Our guest on ST is Petina Gappah, an award-winning, widely translated Zimbabwean writer and lawyer. She joins us to discuss her new novel, which explores the life of David Livingstone, the 19th-century Scottish missionary who famously set out to find the source of the Nile. As was noted of this book, which is called "Out of Darkness, Shining Light: A Novel," in The New York Times Book Review: "Gappah lists at least 30 books in the bibliography of her scrupulously researched new novel. This being