Juan Valera was a Spanish writer, diplomat, and philosopher. He spent six months in St. Petersburg on official duty. This is how his 'Letters from Russia' appeared. In them, Juan Valera captured humorous sketches of St. Petersburg life, diplomatic news, and his reflections on the development of Russian literature from the chronicles to Pushkin and Gogol. Another thing that ties Juan Valera to Russian literature is that Western European critics called him 'the Spanish Turgenev.'

The very title of the novel, 'The Illusions of Doctor Faustino,' alludes to Goethe's famous 'Faust' and hints at the 'lost illusions' in the works of Balzac and Flaubert. But Doctor Faustino is, rather, a miniature Faust. Juan Valera's character is not endowed with extraordinary abilities; he is not visited by the devil or offered immortality. Don Faustino López de Mendoza is an impoverished aristocrat who is overcome by destructive illusions. He graduates from university, receives a doctorate, and struggles to find a place in life. He believes that if he moves to Madrid, he will immediately become an outstanding philosopher, poet, or politician. At the same time, Dr. Faustino strives for ideal love, for which he is willing to sell his soul to the devil. Don Faustino seeks it in the form of his cousin Constancia, the notary's daughter Rosita, and the Eternal Companion—a mysterious stranger who invisibly watches him. Juan Valera destroys the principles of romanticism and allows the ideal to be realized. However, illusions are shattered, and without them, ideal love fades.