Kepler’s mathematical metaphysics was always of interest to, because it is this metaphysics connected astronomy, astrology, religion and yes – C. G. Jung. Kepler believed that the world was created by God to express divine aesthetics, what Kepler called “Archetypes.” This aesthetics was essentially geometrical in nature. If one knows the details of God’s aesthetics, then one can infer a priori certain structural features of the world–for example, whether the world is Copernican or Ptolemaic. Conversely, if one knows the structural features of the world, then one can gain access to God’s aesthetic plan.
To look at Kepler’s astronomy in some detail, of course interesting in its own right. Kepler’s manuscripts have been collected in the Johannes Kepler Gesammelte Werke and Joannis Kepleri astronomi opera omnia. The Mysterium cosmographicum, Apologia pro Tychone contra Ursum, Astronomia nova, Harmonice mundi, selections of Epitome astronomiae Copernicanae, and selections of Kepler’s correspondences have been availible to me into English.