Book excerpt: This fifth and final book in Aidan Nichols' Introduction to Hans Urs von Balthasar series covers Balthasar's prodigious output from the 1940s to his death in 1988, leaving aside the great multi-volume trilogy. Nichols identifies Balthasar's most significant sources, including the Church Fathers (especially Origen, Gregory of Nyssa, Maximus the Confessor, and Augustine), Henri de Lubac, Karl Barth, and Adrienne von Speyr. He, then, guides the reader through Balthasar's works thematically, covering fundamental theological themes (revelation and theology, divine providence, the paschal mystery), Mary and the church, the saints, prayer and mysticism, and Christian literature.