Quite simply, the three major themes in Balzac and the Little Chinese Seamstress are imagination, education, and love.
Why imagination? Well, the two boys in the story find a bunch of banned books that are translated into Chinese. The banned books, of course, are title upon title of classics from the West. Quickly, they begin to read the books, letting their imaginations run wild. This allows them to escape the tragedy of their exile from the city. Ironically, this theme of imagination leads perfectly into the next theme.
Why education? Well, at this point in time, China was in the midst of its "Cultural Revolution" where the government spent its energy on the "re-education" especially of its young people. Because of this, the two boys in the story are "re-educated" and taken from the city into the country. The irony is that they boys receive their true education from the Western classic literature that is banned.
Why love? Well, the two boys (even through all of their trials in exile) fall in love with the daughter of the tailor in the rural area where they are to be "re-educated." Their imagination from reading the books and their flirtation with the "Little Chinese Seamstress" of the title transform their lives.
Therefore, the themes of love and imagination and education that maintain a prominent place in Balzac and the Little Chinese Seamstress.