This is a collection of 19th century German theology available online for reading or download. I will update from time to time. In order to attain a competent overview of this period, I recommend:
Protestant Thought in the Nineteenth Century, vol. 1 and vol. 2
Types of Modern Theology: Schleiermacher to Barth (H. R. Mackintosh)
Protestant Theology in the Nineteenth Century (Karl Barth)
Modern Christian Thought: The Enlightenment and the Nineteenth Century
Introduction to Modern Theology: Trajectories in the German Tradition
An invaluable survey of German universities and theologians was published by Philip Schaff in 1857: Germany: Its Universities, Theology, and Religion.
De Wette, Wilhelm Martin Leberecht
Theodore; or, A Skeptic’s Conversion: History of the Culture of a Protestant Clergyman, vol. 1
Theodore; or, A Skeptic’s Conversion: History of the Culture of a Protestant Clergyman, vol. 2
A System of Christian Doctrine, vol. 1
A System of Christian Doctrine, vol. 2
A System of Christian Doctrine, vol. 3
A System of Christian Doctrine, vol. 4
History of Protestant Theology, vol. 1
History of Protestant Theology, vol. 2
Note: Dorner’s works are currently published through Wipf & Stock.
The History of Israel, vol. 1, fourth edition
The History of Israel, vol. 2, fourth edition
The History of Israel, vol. 3, second edition
The History of Israel, vol. 4, second edition
The History of Israel, vol. 5, second edition
The History of Israel, vol. 6, The Life and Times of Christ
The History of Israel, vol. 7, The Apostolic Age
The History of Israel, vol. 8, The Post-Apostolic Age
Frank, F. H. R. (Franz Hermann Reinhold)
Harless, Gottlieb Christoph Adolf von
Christology of the Old Testament, vol. 1
Christology of the Old Testament, vol. 2
Christology of the Old Testament, vol. 3
Christology of the Old Testament, vol. 4
Commentary on the Psalms, vol. 1
Lichtenberger, Frédéric Auguste (Dean of the Faculty of Protestant Theology at Paris)
Lobstein, Paul (French Ritschlian)
Symbolism: Exposition of the Doctrinal Differences Between Catholics and Protestants
The Development of Theology in Germany Since Kant
The Philosophy of Religion on the Basis of Its History, vol. 1 (Spinoza to Schleiermacher)
The Philosophy of Religion on the Basis of Its History, vol. 2 (Schelling to the Present Day)
The Christian Doctrine of Justification and Reconciliation (2nd edition of the English translation)
Sartorius, Ernst Wilhelm C.
The Doctrine of Divine Love; or, Outlines of the Moral Theology of the Evangelical Church
Brief Outline of the Study of Theology
A Critical Essay on the Gospel of St. Luke
Introductions to the Dialogues of Plato
The Life of Schleiermacher: as unfolded in his Autobiography and Letters, vol. 1
The Life of Schleiermacher: as unfolded in his Autobiography and Letters, vol. 2
The Theology of Schleiermacher: A Condensed Presentation of His Chief Work, “The Christian Faith” (by George Cross)
Note: The Christian Faith, his systematic theology, was published in English in 1928 and is, therefore, still under copyright with T&T Clark.
Schmid, Heinrich
A Translation and Commentary of the Book of Psalms
Commentary on the Epistle to the Hebrews, vol. 1
Commentary on the Epistle to the Hebrews, vol. 2
Various
Selected Discourses by Monod, Krummacher, Tholuck, and Müller