The following materials, all of which appeared before Joseph Ratzinger became Benedict XVI, are essential background for understanding the pope.

John Allen, Pope Benedict XVI (Continuum, 2000; reissued 2005). Allen, a well-known Vatican reporter, has lately foresworn the largely negative tone of this volume and written more favorably about Benedict. But this remains useful as a running criticism of Ratzinger’s thought and work.

Aidan Nichols, O.P., The Thought of Benedict XVI: An Introduction to the Theology of Joseph Ratzinger (Burns & Oates, 1988; reissued 2005). One world-class theologian writes about another. Nichols gives a step-by-step account of Ratzinger’s theological work through the late 1980s.

Joseph Ratzinger, Introduction to Christianity (German edition 1968; Ignatius, 2000). In this book, as in his work at Vatican II, Ratzinger appears as a liberal reformer. After Vatican II and the tumult of the 1960s he moved in a more conservative direction.

Congregation for the Doctrine of the Faith, "Dominus Iesus": On the Unicity and Salvific Universality of Jesus Christ and the Church. This 2000 document (available at www.vatican.va) issued by Ratzinger’s office seemed to pull back from the Catholic Church’s previous statements on openness to non-Catholic Christians and adherents of other religions.

Catechism of the Catholic Church (Doubleday, 1995). Ratzinger was a key figure in the development of this catechism.

The Lutheran World Federation and the Roman Catholic Church, Joint Declaration on the Doctrine of Justification (Eerdmans, 1999). Ratzinger’s familiarity with Lutheran theology and his friendship with Lutheran theologians and pastors helped bring about this ecumenical achievement.