Take these as essential ingredients: Satan, Jesus, Stalin, Pontius Pilate and Caesar's Empire, assorted literary critics, a great Artist and the woman who loves him, life in 1930s Moscow, a poet on the bitter road to truth, and various demonic henchmen including a big black cat. They add up to one of the greatest novels of the 20th Century, and one of the handful of most moving books I've ever encountered.
The fundamental purpose of Bulgakov's magnum opus is to hold up the harsh light of truth to the sins and hypocrisies of Stalinist Russia. There are three storylines here: one of them concerns the misadventures of Satan's retinue as they wreak havoc on Muscovite literary society, and presents some of the most penetrating satirical writing you'll ever come across; the second storyline centers around the fifth procurator of Judea, the equestrian Pontius Pilate, and his fateful encounter with Jesus leading to the latter's crucifixion; the final story presents the fates of a great writer (the master), and his lover (Margarita). Bulgakov brings the three stories together in a demonstration of narrative genius, to bury the oppressive fallacy of Soviet society and ideals beneath the combined forces of good and evil, of love, of freedom, and of magic and mysticism.
One brief note about available translations: after sampling most of the available English translations, I am firmly convinced that the Pevear/Volkhonsky version is far and away the best. The notes are excellent, and the introduction by Richard Pevear gives invaluable insight into the history of the novel and its ideas. But most of all, they give the narrative much greater vividness and depth, especially in the wonderfully lyrical Pilate chapters. This translation of Bulgakov's most remarkable novel is enthusiastically recommended!