The Magic Mountain contains many contrasts and parallels with the earlier novel. Gustav von Aschenbach, an established author, is matched to a young, callow engineer at the start of a regular career. The erotic allure of the beautiful Polish boy Tadzio corresponds to the Asiatic-flabby ("asiatisch-schlaff") Russian Madame Chauchat. The setting was shifted both geographically and symbolically. The lowlands of the Italian coastlands are contrasted to an alpine resort famed for its health-giving properties.

Mann describes the subjective experience of serious illness and the gradual process of medical institutionalization. He also alludes to the irrational forces within the human psyche, at a time when Freudian psychoanalysis was becoming a prominent type of treatment. These themes relate to the development of Castorp's character over the period covered by the novel. In his discussion of the work, written in English and published in The Atlantic in January 1953, Mann states that "what [Hans] came to understand is that one must go through the deep experience of sickness and death to arrive at a higher sanity and health...".

Mann acknowledged his debt to the skeptical insights of Friedrich Nietzsche concerning modern humanity, and he drew from these in creating conversations between the characters. Throughout the book, the author employs the discussions among Settembrini, Naphta, and the medical staff to introduce the young Castorp to a wide spectrum of competing ideologies about responses to the Age of Enlightenment. However, whereas the classical Bildungsroman would conclude by Castorp's having become a mature member of society, with his worldview and greater self-knowledge, The Magic Mountain ends with Castorp's becoming an anonymous conscript, one of millions, under fire on some battlefield of World War I.