In Darkest Africa: Or, the Quest, Rescue and Retreat of Emin, Governor of Equatoria by Henry Morton Stanley.  
 
On 28 October 1888 the Welsh-American explorer Henry Morton Stanley was entrenched deep in the unexplored Ituri rainforest of the Congo. He had been hacking his way back and forth through the jungle for months in his attempt to relieve the colonial governor Emin Pasha, whose province in the southern Sudan was under siege by a coalition of Sudanese and Arab insurgents under the command of the messianic cleric Muhammad Ahmad. Famished and exhausted, Stanley sent his East-African porters out to pillage what they could from native farms.  
 
Eventually persuaded by Stanley, they proceeded to the Indian Ocean by way of the Semliki River which was found to connect Lake Albert with Lake Edward.  
 
Stanley’s own melodramatic account of the Emin Pasha Relief Expedition, In Darkest Africa, sold 150,000 copies in 1890 alone and was translated into ten European languages.