LOURDES OF THE THREE CITIES

Émile Zola wrote a novel titled Lourdes which is indeed part of his The Three Cities Trilogy (Les Trois Villes in French) but the exact title you've mentioned Lourdes of the Three Cities doesn't correspond to any known specific work by Zola. Lourdes is the first book in Zola's trilogy and focuses on the town of Lourdes examining the religious fervor and pilgrimage associated with the miraculous events reported there. The trilogy also includes Rome and Paris which similarly explore the themes of faith social issues and the interplay between different elements of society in those cities. Zola's Lourdes particularly investigates the clash between religious faith commercial interests scientific skepticism and the complexities of human beliefs. It centers on the experiences of various characters including pilgrims doctors clergy and merchants providing a critical examination of the impact of religious phenomena on society. While Lourdes is indeed a part of Zola's The Three Cities Trilogy there doesn't seem to be a separate work titled Lourdes of the Three Cities specifically attributed to Zola. If you have further details or specifics I'd be glad to assist further!