The most significant theme in the novel is the struggle between good and evil. Characters are described explicitly as either angels or devils. Some of the devil characters are Chief Inspector Fumero, whose murderous escapades make him infamous and universally feared, and Laín Coubert, the mad, fire-scarred avenger and destroyer of Julián Carax’s books.

One of the angel characters is Jacinta Coronado’s prophetic dark angel Zacaríus. Daniel frequently characterizes the women in his life, from his mother, to Clara Barceló and Bea, as angels.

This device is used as a technique of magical realism, when characters are depicted as having “visions” of angels or devils. For example, Jacinta receives many visions and prophecies from Zacaríus, but at times, she questions whether he is real or not. The physical fights, as between Fumero and Lain Coubert, are improbable. Julian Carax is a weakened, nearly dead man, but he summons superior strength when he overcomes Fumero and flings his body onto the spiky arm of the broken angel in the fountain, killing Fumero. That symbolism demonstrates that only a devil can kill another devil.

Angels are typically fallen ones in this novel, with the exception of Daniel’s mother, who comes to him when he dies, possibly saving him.