The scope of Petina Gappah’s impressive novel is laid out in the prologue: the death of the Victorian explorer David Livingstone and the ferrying of his desiccated body by loyal servants to the East African coast, so it could be returned in glory to his native Britain. A passage in Herodotus sent Livingstone on a fruitless search for four mythical fountains which he believed were the source of the Nile.