Through the first-person narration of Gabriel de Araceli, the novel describes the second siege of Zaragoza, which occurred in January and February 1809, during the War of Independence between Spain and France. The story depicts one of his most stark pictures of the violence of the war, with meticulous descriptions of the preparations for the defense of the city, under General Palafox, the war skirmishes, the lack of food, the technical and material superiority of the French and the yellow fever epidemic that decimated the population of a Zaragoza.

Benito Pérez Galdós (1843-1920) was a Spanish realist novelist. Some authorities consider him second only to Cervantes in stature as a Spanish novelist. He was the leading literary figure in 19th-century Spain. He remains popular in Spain, and is considered as equal to Dickens, Balzac and Tolstoy. While his plays are generally considered to be less successful than his novels, Realidad is important in the history of realism in the Spanish theatre.