After almost twenty-seven years of his pontificate, what was John Paul II's legacy regarding the ministerial priesthood? What answers did he give to the questions still surrounding this reality today? Nilson Leal de Sá, CB, examines the pontiff's twenty-seven letters of Holy Thursday addressed annually to the priests. Unlike some papal documents, which are drafted by many hands, these letters to priests were born of a personal initiative, wherein the pope spoke ab imo pectore (from the depths of his heart), giving a little of himself and his thought. Cardinal Georges-Marie Cottier, theologian emeritus of the Pontifical House and a connoisseur of the texts of the Holy Father, has confirmed that "the Letters of Holy Thursday were written by John Paul II himself." Leal de Sá has sought in the diversity of the letters of Holy Thursday the major points of the thought of John Paul II on this important topic. The first chapter dwells on the sources of his teaching and emphasizes his use of the Word of God, Tradition, and the conciliar Magisterium. These foundations are the basis of the second chapter, which highlights the priestly identity in the life of the Church. Finally, the third chapter elucidates the specific mission of the priest. The Priesthood, Mystery of Faith presents itself as a real and stimulating synthesis of John Paul II's thought about the ministerial priesthood in a systematic way. It renews us in the appreciation of the inestimable gift that God makes to the whole Church through the sacrament of the Holy Orders.