One of the main themes is loneliness. Otto seems isolated at first, but as the story progresses, his interactions start to change that. Another theme could be redemption. His past actions or attitudes might be redeemed through new relationships.
The novel 'A Man Called Otto' likely has themes of love and loss. Otto may have experienced loss in his past, which has made him the way he is. And as he encounters new people, there is an element of love that starts to seep into his life, whether it's friendship or something more, which helps him to transform.
Well, themes like the power of community are quite prominent. In 'A Man Called Otto Novel', Otto is a bit of a loner, but the community around him gradually draws him in. Also, the theme of acceptance is there. He has to accept the changes in his life and the people around him.