- Loughlin, Stephen J. Aquinas’ Summa Theologiae: A Reader’s Guide. T&T Clark Reader’s Guides. London; New York: T&T Clark, 2010.
- Schakel, Peter J. The Way into Narnia: A Reader’s Guide. Grand Rapids, MI; Cambridge, U.K.: William B. Eerdmans Publishing Company, 2005.
- McKim, Donald K. John Calvin: A Companion to His Life and Theology. Vol. 25. Cascade Companions. Eugene, OR: Cascade Books, 2015.
- Congdon, David W. Rudolf Bultmann: A Companion to His Theology. Cascade Companions. Eugene, OR: Cascade Books, 2015.
- Radde-Gallwitz, Andrew. Basil of Caesarea: A Guide to His Life and Doctrine. Vol. 16. Cascade Companions. Eugene, OR: Cascade Books, 2012.
- Pecknold, C. C. Christianity and Politics: A Brief Guide to the History. Vol. 12. Cascade Companions. Eugene, OR: Cascade, 2010.
- Elliott, John H. Conflict, Community, and Honor: 1 Peter in Social-Scientific Perspective. Cascade Companions. Eugene, OR: Cascade Books, 2007.
- Riswold, Caryn D. Feminism and Christianity: Questions and Answers in the Third Wave. Cascade Companions. Eugene, OR: Cascade Books, 2009.
- Bash, Anthony. Forgiveness: A Theology. Vol. 19. Cascade Companions. Eugene, OR: Cascade Books, 2015.
- Hunt, Hannah. A Guide to St. Symeon the New Theologian. Cascade Companions. Eugene, OR: Cascade Books, 2015.
- Byassee, Jason. An Introduction to the Desert Fathers. Cascade Companions. Eugene, OR: Cascade Books, 2007.
- Brian, Rustin E. Jacob Arminius: The Man from Oudewater. Vol. 17. Cascade Companions. Eugene, OR: Cascade Books, 2015.
- McKim, Donald K. John Calvin: A Companion to His Life and Theology. Vol. 25. Cascade Companions. Eugene, OR: Cascade Books, 2015.
- deSilva, David A. The Letter to the Hebrews in Social-Scientific Perspective. Vol. 15. Cascade Companions. Eugene, OR: Cascade Books, 2012.
- Byassee, Jason. Reading Augustine: A Guide to the Confessions. Cascade Companions. Eugene, OR: Cascade Books, 2006.
- Kelly, Geffrey B. Reading Bonhoeffer: A Guide to His Spiritual Classics and Selected Writings on Peace. Vol. 6. Cascade Companions. Eugene, OR: Cascade Books, 2008.
- Skinner, Christopher W. Reading John. Cascade Companions. Eugene, OR: Cascade Books, 2015.
- Gorman, Michael J. Reading Paul. Cascade Companions. Eugene, OR: Cascade Books, 2008.
- Littlejohn, W. Bradford. Richard Hooker: A Companion to His Life and Work. Cascade Companions. Eugene, OR: Cascade Books, 2015.
- Ferguson, Everett. The Rule of Faith (A Guide). Vol. 20. Cascade Companions. Eugene, OR: Cascade Books, 2015.
- Johnson, Dru. Scripture’s Knowing: A Companion to Biblical Epistemology. Cascade Companions. Eugene, OR: Cascade Books, 2015.
- Fowl, Stephen E. Theological Interpretation of Scripture. Cascade Companions. Eugene, OR: Cascade Books, 2009.
- Castelo, Daniel. Theological Theodicy. Vol. 14. Cascade Companions. Eugene, OR: Cascade Books, 2012.
- Long, D. Stephen. Theology and Culture: A Guide to the Discussion. Cascade Companions. Eugene, OR: Cascade Books, 2008.
- Dillard, Peter S. A Way into Scholasticism: A Companion to St. Bonaventure’s the Soul’s Journey into God. Vol. 13. Cascade Companions. Eugene, OR: Cascade Books, 2011.
- McColman, Carl. Befriending Silence: Discovering the Gifts of Cistercian Spirituality. Notre Dame, IN: Ave Maria Press, 2015.
- Osborne, Kenan B. The Christian Sacraments of Initiation: Baptism, Confirmation, Eucharist. New York; Mahwah, NJ: Paulist Press, 1987.
- Ditewig, William T. The Deacon at Mass: A Theological and Pastoral Guide. Second Edition. New York; Mahwah, NJ: Paulist Press, 2013.
- Dimech-Juchniewicz, Jean. Facing Infertility: A Catholic Approach. Boston, MA: Pauline Books & Media, 2012.
- Jackson, L. Charles. Faith of Our Fathers: A Study of the Nicene Creed. Moscow, ID: Canon Press, 2007.
- Schreck, Alan. The Legacy of Pope John Paul II: The Central Teaching of His 14 Encyclical Letters. Steubenville, OH: Emmaus Road Publishing, 2012.
Do you intend for introductions to theologians and such (i.e. books to be read before reading the actual works of) to be considered study guides? I'm thinking of the "A Guide for the Perplexed" and the "Armchair Theologian" series.