Set in 'German Central Africa' (a slightly disguised and fictional version of German East Africa) and written in 1935, THE AFRICAN QUEEN is probably one of C S Forester's best known non-HORNBLOWER novels. The plot is vaguely based on the story of the Royal Navy's Spicer-Simson Expedition, which saw two motor boats – named Mimi and Toutou – transported first to South Africa and then by railway, by river, and road through the African jungle to Lake Tanganyika in order to sink (or capture) the German lake gunboats Kingani, Hedwig von Wissman, and Graf von Götzen.
The book tells the story of Rose Sayer's and Charlie Allnutt's journey down the Ulanga/Bora River to sink the German gunboat Königin Luise. Rose is the sister of a British missionary who dies a broken man when his 'flock' is forcibly conscripted to serve the needs of the Germans, and Allnutt is a Cockney engineer who works at a Belgian mine fixing the machinery and operating their supply launch, the African Queen.
It is a tale of revenge, fortitude, ingenuity, and unlikely love between two lonely people. The book was made into a film (starring Humphrey Bogart as Charlie Allnutt and Katharine Hepburn as Rose Sayer) in 1951, and although the ending is slightly different, the main plot remains the same.