"The purpose and the meaning of my journey were never quite clear to me," admits British-born, Arizona-based travel writer Richard Grant in the introduction to his unsettling account of a chaotic trip across east Africa. It's an inauspicious start, but Grant manages to make a virtue of the pointlessness of his mission to become the first man to run the whole of Tanzania's Malagarasi river, just about persuading the reader that his encounters with a picaresque parade of prostitutes and chancers justifies a whole book. Fortunately, too, Grant combines the natural danger-seeking ego of the travel writer with a quiet empathy for ordinary people struggling to lead decent lives, while his experiences in Rwanda and Burundi lead him to raise difficult and important questions about the efficacy of foreign aid, the economic impact of Chinese investment and the radioactive half-life of the genocide. Grant is also rescued from ersatz fear-and-loathing territory by his ability to capture the harshness of nature and the vulnerability of the human body in an environment swarming with potential threats, whether human, animal or bacterial. Grimly entertaining but mostly just grim, it's enough to make armchair travellers lay their heads on their antimacassars with heartfelt gratitude.