Haggard wrote the novel as a result of a five-shilling wager with his brother, who said that he could not write a novel half as good as Robert Louis Stevenson's Treasure Island (1883). He wrote it in a short time, somewhere between six and sixteen weeks between January and 21 April 1885. However, the book was a complete novelty and was rejected by one publisher after another. After six months, King Solomon's Mines was published, and the book became the year's best seller, with printers struggling to print copies fast enough.
In the process, King Solomon's Mines created a new genre known as the "Lost World", which would inspire Edgar Rice Burroughs' The Land That Time Forgot, Arthur Conan Doyle's The Lost World, Rudyard Kipling's The Man Who Would Be King and H. P. Lovecraft's At the Mountains of Madness. In The Return of Tarzan (1913), Edgar Rice Burroughs introduced his own lost city of Opar, in which the influence of King Solomon's Mines is evident (Burroughs' Opar is supposedly the same the Biblical Ophir with which King Solomon traded). Opar reappeared in further Tarzan novels and was later taken up in the Khokarsa novels of Philip José Farmer and various derivative works in other media. Burroughs also introduced other lost cities in various hidden corners of Africa, for Tarzan to visit, such as a valley inhabited by stray Crusaders still maintaining a Medieval way of life. Robert E. Howard's Conan the Barbarian also visited several lost cities, and Lee Falk's The Phantom was initially written in this genre. A much later Lost World novel is Michael Crichton's Congo, which is set in the 1970s and features characters seeking a trove of diamonds in the lost city of Zinj for use in electronic components rather than jewellery.
As in Treasure Island, the narrator of King Solomon's Mines tells his tale in the first person in an easy conversational style. Almost entirely missing (except in the speech of the Kukuanas) is the ornate language usually associated with novels of this era. Haggard's use of the first person subjective perspective also contrasts with the omniscient third-person viewpoint then in vogue among influential writers such as Anthony Trollope, Thomas Hardy, and George Eliot.
The book has scholarly value for the colonialist attitudes that Haggard expresses, and for the way that he portrays the relationships between the white and African characters. Haggard portrays some African characters as barbarians, such as Twala and Gagool, but their barbarity has more to do with their roles as antagonists in the story than with their African heritage. He also presents the other side of the coin, showing some black Africans as heroes and heroines (such as Ignosi), and showing respect for their culture. The book expresses much less prejudice than some of the later books in this genre. Indeed, Quatermain states that he refuses to use the word "nigger" and that many Africans are more worthy of the title of "gentleman" than the Europeans who settle or adventure in the country. Haggard even includes an interracial romance between a Kukuana woman, Foulata, and the white Englishman Captain Good. The narrator tries to discourage the relationship, dreading the uproar that such a marriage would cause back home in England; however, he has no objection to the lady, whom he considers very beautiful and noble. Haggard eventually kills off Foulata, who dies in Good's arms.
Kukuanaland is said in the book to be forty leagues north of the Lukanga river in modern Zambia, which would place it in the extreme southeast of the present Democratic Republic of Congo. The culture of the Kukuanas shares many attributes with other South African tribes, such as Zulu being spoken and the kraal system being used.