Ferris is met geen enkel ander jeugdboek te vergelijken, zoals ook de personages en de gebeurtenissen met niets of niemand te vergelijken zijn. Zelfs niet met personages en gebeurtenissen uit andere boeken van DiCamillo. En daarom is Ferris ook een echte DiCamillo.
Volgens Wikipedia: Many of the books follow someone who is alone and has to survive on their own, undergoing suffering and loneliness,[57] commonly the absence or loss of parents.[8][58] The author Julie Schumacher said that "a sense of abandonment [...] pervades everything she has written."[57] Other themes in DiCamillo's novels include love, salvation, emotional change, and "senseless cruelty", according to the New York Times.[8][59] According to the Journal of the American Academy of Child and Adolescent Psychiatry, DiCamillo's works often begin with young protagonists who are "puzzled, wanting, and waiting" but conclude that they must handle matters on their own.[60]
