Sigrid Undset is best known for Kristin Lavransdatter, which is weighty and detailed enough to serve as a life’s work. But she also wrote more novels—most notably the Master of Hestviken tetralogy–and several hagiographies.
Her biography of Catherine of Siena is well worth reading. Consider this quote, which argues that we need to understand the nature and teleology of man before we can decide what his rights or form of government must be:
The artificial division of religion and politics did not exist for the people of the Middle Ages. If they thought over the matter at all, they were completely aware that all the problems concerning the community—good or bad government, the welfare or misery of the people—are in the final instance religious problems. The fundamental question is, What do we believe a man to be? What is it he needs, first and foremost, so that he may be in a position to attain all his secondary needs—peace, justice, security, satisfactory relationships with his fellow men?(Sigrid Unset, Catherine of Siena, 127)