(Warning: Beware the used or library textbook with highlighting. Do the human race a favor and don't highlight your books.)
Markus, R.A., The End of Ancient Christianity, Cambridge, 1991.
Pernoud, Regine, Those Terrible Middle Ages: Debunking the Myths, Ignatius, 2000.
Evans, G.R., Philosophy and Theology in the Middle Ages, Routledge, 1993.
George, Timothy, Theology of the Reformers, Broadman & Holman, 1988.
Hillerbrand, Hans J., ed., The Protestant Reformation. Harper & Row, 1968.
Matheson, Peter, The Imaginative World of the Reformation, Fortress, 2001.
Selected primary-source readings in medieval theology (on-line).
Recommended/extra credit reading:
F.L. Cross, The Oxford Dictionary of the Christian Church, 2nd ed. or 3rd ed., Oxford, 1983 or 1997 .
Richard A. Muller, Dictionary of Latin and Greek Theological Terms, Baker, 1985.
Reinhold Seeberg, The History of Doctrines. Baker, 1979.
William C. Placher, A History of Christian Theology, Westminster, 1983.
Peter Brown, Augustine of Hippo: A Biography, rev. ed., University of California, 2000 ; or Henry Chadwick, Augustine: A Very Short Introduction, Oxford, 2001.
Fernandez-Armesto, Felipe and Wilson, Derek, Reformations: A Radical Interpretation of Christianity and the World, 1500-2000, Scribner, 1996.
Carter Lindberg, The European Reformations, Blackwell, 1996.
Richard A. Muller, The Unaccommodated Calvin, Oxford, 2000.
Heiko A. Oberman, Martin Luther: Man Between God and the Devil, Image, 1992.
Heiko A. Oberman, The Reformation: Roots and Ramifications, Eerdmans, 1994.
David C. Steinmetz, Luther in Context, 2d ed., Baker, 2002.
David C. Steinmetz, Reformers in the Wings: from Geiler von Kaysersberg to Theodore Beza, 2d ed., Oxford, 2001.
For students improving their writing skills, my classes feature conditionally required reading.