King Solomons Mines by H. Rider Haggard

Allan Quatermain, an adventurer and white hunter based in Durban, in what is now South Africa, is approached by aristocrat Sir Henry Curtis and his friend Captain Good, seeking his help finding Sir Henrys brother, who was last seen travelling north into the unexplored interior on a quest for the fabled King Solomons Mines. Quatermain has a mysterious map purporting to lead to the mines, but had never taken it seriously. However, he agrees to lead an expedition in return for a share of the treasure, or a stipend for his son if he is killed along the way. He has little hope they will return alive, but reasons that he has already outlived most people in his profession, so dying in this manner at least ensures that his son will be provided for. They also take along a mysterious native, Umbopa, who seems more regal, handsome and well-spoken than most porters of his class, but who is very anxious to join the party.