In his inaugural Mass on Sunday, newly elected Pope Leo XIV, looking out at crowds of world leaders and broadcasting to millions worldwide, made clear his aim to be a voice for "love and unity," as charged by Jesus to St. Peter and by his namesake, Pope Leo XIII, to all. His homily concluded: “Brothers and sisters, this is the hour for love! The heart of the Gospel is the love of God that makes us brothers and sisters. With my predecessor Leo XIII, we can ask ourselves today: If this criterion ‘were to prevail in the world, would not every conflict cease and peace return?’ ”

How the pan-American Cardinal Robert Francis Prevost, a citizen of the US and Peru, now the shepherd of 1.4 billion Catholics, arrived at this moment, this vision, might be gleaned in two new books released this month.

Leo XIV: Portrait of the First American Pope, went on sale today. The biography, published by the Catholic channel EWTN, was written by historian Matthew Bunson, VP and editorial director for EWTN. And James Bacik's Catholic Social Teaching, published May 6 by Paulist Press, details the theological underpinning of the church's views on society, economics, and human dignity. Both Bunson and Paulist president and publisher Paul McMahon expect these themes will be central to Leo XIV's papacy.

Bunson details the life story of a Chicago youth steeped in St. Augustine's teaching. Prevost joined the Augustinian order of priests, rose through the church ranks beginning as a missionary in Peru, and was elevated to Cardinal and key Vatican administrator by Francis in 2023. "But he's not Francis II," Bunson said. "In almost every speech he gives he's pulling from all the recent saints, so all the recent Popes, the Vatican Council" and more.

How far back does the new Pope Leo harken? The first Pope Leo was called Leo the Great for staring down Atilla the Hun and saving Rome from destruction, says the historian. Look next to Leo XIV. Bunson says this pope confronted the challenges of his time—the impact of the Industrial Revolution and the rise of socialism on workers, families, and society—in his 1891 encyclical Rerum Novarum (Of New Things). This still stands today as the foundation of Catholic social teachings and it was the source of the quote in the pope's homily Sunday. Bunson projects that the new pope will see AI as the revolution of our time and he will have "a significant focus on technology and its impact on culture and the human person."

Of the new pope, McMahon of Paulist Press told PW: "People are going to be watching for his first encyclical, his comments on social justice and on immigration." He said he suspects that the first encyclical will be based on Leo XIV's Rerum Novarum, which was written by a pope who saw "the rights of workers being pushed aside for profitability and capitalism and he fought back against that."

In addition to Catholic Social Teaching, Paulist is commissioning a look at Vatican II, another critical event that McMahon expects will be influential in the new pope's thinking. That book, by Fr. Thomas Rausch, is planned for spring 2026.

This article has been updated with further information.