As a novelist, Eggen made his debut with an about the life and death of general Carl Gustav Fleischer, the Norwegian commander in chief at Narvik 1940. He also wrote a portrait of the writer Agnar Mykle, his father-in-law and has written novels with topics from medieval Norway. In 1993 Eggen published "The boy from Gimle"—the autobiographical story of a Norwegian childhood in a Nazi milieu. As a consequence, two years later the Norwegian war children got an official excuse.