Since first reading Stringfellow's pivotal book I've read and drawn upon Walter Wink's Powers trilogy, but almost nothing has hit me in the gut the way An Ethic did. Here are the basic three in Wink’s triad, as well as a link for a 4th, related but shorter book:
Volume 1: Naming the Powers: The Language of Power in the New TestamentIn addition, for all time: Martin Buber, I and Thou,
Volume 2: Unmasking the Powers: The Invisible Forces That Determine Human Existence
Volume 3: Engaging the Powers: Discernment and Resistance in a World of Domination
one volume, sort of, but mainly a condensation or digest of volume 3:
Engaging the Powers: The Powers That Be: Theology for a New Millennium
the triad of sermons by Paul Tillich: The Shaking of the Foundations, The Eternal Now and The New Being;
Anthony Padovano, Dawn Without Darkness: A Trilogy on the Spiritual Life, Including Belief in Human Life and Free to Be Faithful, a slender volume illustrated with exquisite photographs and published by Paulist Press (always a favorite),
Richard Niebuhr's Christ and Culture [Christ Against Culture; Christ of Culture; Christ Above Culture; Christ and Culture in Paradox; and Christ the Transformer of Culture.]
Since I'm writing about books, here's my Amazon Wish List!