That work is titled Doctor Faustus.
One of his last works is narrated by Serenus Zeitblom, who describes his friend Adrian  Leverkuhn's deal with the devil and his rise to and later fall from greatness. That work is titled Doctor Faustus. In one novel by this author, Hans Castorp stays in the sanatorium for seven years, and one novella by this author sees Gustav von Aschenbach attracted to a Polish boy in the titular city. For 10 points, identify this author of The Magic Mountain and Death in Venice.
One of his last works is narrated by Serenus Zeitblom, who describes his friend Adrian  Leverkuhn's deal with the devil and his rise to and later fall from greatness.
Thomas Mann