Demianis a coming-of-age story that follows a young boy's maturation as he grapples with good and evil, lightness and darkness, and forges alternatives to the ever-present corruption and suffering that he sees all around him. Crucial to this development are his relationships with a series of older mentors, of who the titular Demian is the most charismatic, otherworldly and ultimately influential.

Many have noted the influence of Jungian psychology upon this novel and it is fascinating to see Herman Hesse's interests in the self, existence and free will play out through through the lens of early twentieth-century Europe; Christian imagery and themes are ever-present, as is the shadow of the First World War.