Complex sentence: The breadth of his intellectual interests was illustrated by his library, which was catalogued after his death and was found to comprise nearly 600 titles including over 475 humanistic and literary works, focusing primarily on philosophy and theology, as well as music treatises and works.
Split into simpler sentences: The breadth of his intellectual interests was illustrated by his library, which was catalogued after his death. It was found to comprise nearly 600 titles including over 475 humanistic and literary works, focusing primarily on philosophy and theology, as well as music treatises and works.