In this collection of essays newly published in English, Volker Leppin restores a holistic understanding of Martin Luther's development amid a late-medieval context strongly influenced by mysticism. Far from marking a clean break from earlier ideas, Luther's emerging theology drew upon deep wells of both personal mystical experience and the guidance of earlier mystics. Meister Eckhart's student, the fourteenth-century priest and theologian John Tauler, was an especially important source of inspiration for the young Luther, though he was also an avid student of figures such as Bernard of Clairvaux. Leppin's careful research overturns conceptions of late-medieval mysticism as inherently works-oriented, illuminating instead how Tauler and others influenced Luther's emerging views on indulgences, the Passion, the Eucharist, and theological tenets including the concepts of law and gospel, justification, and the priesthood of all believers. United with Christ continues to expand upon threads drawn in Leppin's 2024 Sola: Christ, Grace, Faith, and Scripture Alone in Martin Luther's Theology , helping us understand the emergence of the Reformation as an innovative series of developments from, rather than an absolute rupture with, late-medieval Christianity.