What is the theme in The Baron in the Trees by Italo Calvino?

Another theme is the value of the unexpected. Cosimo does not set out to be shocking, only to be the master of his own destiny, but the nature of his chosen path does make him rather a conspicuous character among the people of Ombrosa and greater Italy. This is exactly what makes it possible for him to exercise the kind of influence he does. People pay particular attention to him because he is such a singular character. Things that start out as strange to their perception became quite normal because he normalizes them. Another aspect of the value of the unexpected is perhaps best demonstrated whenever it is necessary for Cosimo to operate covertly.