Heart of Darkness
Heart of Darkness (1899) is a novella by Polish-English novelist Joseph Conrad about a narrated voyage up the Congo River into the Congo Free State in the so-called "heart of Africa". Charles Marlow, the narrator, tells his story to friends aboard a boat anchored on the River Thames. This setting provides the frame for Marlow's story of his obsession with the ivory trader Kurtz, which enables Conrad to create a parallel between what Conrad calls "the greatest town on earth", London, and Africa as places of darkness.
Heart of a Dog
Heart of a Dog (, "Sobachye syerdtsye") is a novel by Russian author Mikhail Bulgakov. A biting satire of Bolshevism, it was written in 1925 at the height of the NEP period, when communism appeared to be relaxing in the Soviet Union. 
It is generally interpreted as an allegory of the Communist revolution and "the revolution's misguided attempt to radically transform mankind." Its publication was initially prohibited in the Soviet Union, but it circulated in samizdat until it was officially released in the country in 1987. It is "one of novelist Mikhail Bulgakov's most beloved stories" featuring a stray dog "named Sharik who takes human form" as a slovenly and narcissistic incarnation of the New Soviet man.
The novel has become a cultural phenomenon in Russia, known and discussed by people "from schoolchildren to politicians."
It has become a subject of critical argument, was filmed in both Russian and Italian-language versions, and was adapted in English as a play and an opera.