Every leader stamps the organization he or she leads with his or her own unique personality. It matters little if that organization is a global superpower or a girls' softball team. When the organization in question is the two-thousand-year-old Catholic Church, the leader's personality not only reaches every corner of earth but also touches the edges of eternity. If we want to pluck the chords that produce the melody of the pope's personality, we must learn what tugs at Pope Francis's heartstrings. Pope Francis has welcomed the world into his heart by composing four major documents over the course of his five-year pontificate. In each one, he reveals another layer of his papal personality. In the first one, Lumen fidei (The Light of Faith), the pope shares how faith illuminates the Christian's path not only with Christ's light but also with his love and mercy. In the second, Evangelii gaudium (The Joy of the Gospel), he insists that without joy a Christian cannot effectively share the good news of Christ. You can catch more flies with honey than vinegar. The third document, Laudato si' (Praised Be to You), depicts the pontiff as a fearless and forthright defender of God's creation. Finally, in the fourth document, Amoris laetitia (The Joy of Love), the pope offers a recipe for how Christian family life can be a haven of joy and grace even in the face of difficulties like divorce. Oh, Lord, Have Mercy provides a fresh approach to attune American Catholic's ears to hear the melody of the pope's heart. Organized by chapters according to the pope's four documents, these homilies will help anyone appreciate the papal personality that is shaping and stamping itself upon the world's largest Christian Church.