This is the metaphysical library; there are many things to behold.

Heresy is marked (H), while potential heresy is marked (PH). Pagan texts are marked (P).

Apostolic:

The Shepherd of Hermas

Clement of Rome: First Epistle to the Corinthians

Clement of Rome: Second Epistle

Ignatius of Antioch: Epistle to the Romans

Justin Martyr: First Apology

Patristic:

Ambrose: On the Holy Spirit

Athanasius: The Life of St. Anthony

Athanasius: On the Incarnation of the Word

Augustine: Against Faustus

Augustine: Concerning Faith of Things Not Seen

Augustine: Confessions

Augustine: City of God

Augustine: Enchiridion

Augustine: On the Trinity

Basil the Great: Nine Homilies of the Hexameron

Clement of Alexandria: Paedogogus

Gregory of Nyssa: On the Soul and the Resurrection

Jerome: Letter 3 (To Rufinus the Monk)

Jerome: Letter 22 (To Eustochium)

John Chrysostom: Sermons on the Gospel of John

John Chrysostom: Sermons on the Gospel of Matthew

John Chrysostom: Three Homilies on the Power of Satan

Methodius: The Banquet of the Ten Virgins

Origen: Against Celsus (H)

Origen: De Principiis (H)

Pseudo-Dionysius: Celestial Hierarchies (PH)

Pseudo-Dionysius: On the Divine Names (PH)

Pseudo-Dionysius: Mystical Theology

Tertullian: On the Flesh of Christ

Early Medieval

Boethius: The Consolation of Philosophy 

John Scotus Eriugena: Coming Soon

High Medieval:

Anselm: Proslogium; Monologium; An Appendix in Behalf of the Fool by Gaunilon; and Cur Deus Homo

Bernard of Clairvaux: On Loving God

Bonaventure: The Mind’s Road to God

Duns Scotus: A Treatise on God as the First Principle

Francis of Assisi: Canticle of the Sun

Francis of Assisi: Praises

Hildegard von Bingen: Coming Soon

Johannes Tauler: Inner Way

Marguerite Porete: Mirror of Simple Souls (H)

Nicholas of Cusa: Coming Soon

Thomas Aquinas: Summa Theologica

Late Medieval and Renaissance

Theologia Germanica

Girolamo Savonarola: Wretched am I

Meister Eckhart: Sermons (PH)

Pico della Mirandola: Oration on the Dignity of Man (H)

Thomas a Kempis: Imitation of Christ

Byzantine:

Gregory Palamas: Triads

John Damascus: Apologia Against Those Who Decry Holy Images

John Damascus: An Exact Exposition of the Orthodox Faith

Pseudo-Methodius: Apocalypse

Maximus the Confessor: 400 Chapters on Love

Judaic:

The Kabbalah Unveiled (PH)

Maimonides: A Guide for the Perplexed

Philo: On the Confusion of the Tongues

Philo: On Creation

Pre-Socratic (P):

Heraclitus: Fragments

Parmenides: Fragments

Pythagoras: Fragments

Xenophanes: Fragments

Plato (P):

Apology

Crito

Euthryphro

Ion

Parmenides

Phaedo

Phaedrus

The Republic

Symposium

Timaeus

Aristotle (P):

Categories

Metaphysics

Nicomachaen Ethics

Posterior Analytics

Prior Analytics

Physics

Hellenistic (P):

Cicero: Dream of Scipio

Cicero: On the Ends of Good and Evil

Cicero: On the Nature of the Gods

Corpus Hermeticum

Marcus Aurelius: Meditations

Sextus Empiricus: The Outline of Pyrronism

Neoplatonic (P):

Plotinus: Enneads

Gnostic (H):

Apocalypse of Peter

Gospel of Judas

Gospel of Thomas

On the Origin of the World

Pistis Sophia

The Mandaean John-Book

Manichaean Psalm to Jesus I