What was Thomas Mann's most influential novel?

Thomas Mann's most influential novel was Existence and Time. This novel is regarded as one of the greatest works in the history of world literature in the 20th century. It explored the philosophical issues of existence and time and deeply influenced the German philosopher Nietzsche and modern metaphysics, cognitive science, and information theory. The novel centers on the protagonist, Castep, and through his experiences, it shows the nature and significance of human existence, and also probes into the nature of time and the role of human beings in it. The novel has been widely translated into many languages and has been adapted into films, stage plays, musics and other art forms. It has had a profound impact on global literature and culture.