This document lays a blueprint for the activity and teaching of John Paul II's pontificate, exploring contemporary human problems and proposing solutions rooted in a deeper understanding of the person--both of the human person, and that of Christ. Significant topics include: a critique of atheistic governments and the right to religious freedom; a missionary message; an affirmation of Christ's union with each person; the value of technological progress; and the imbalance of economic resources.
The Holy Father gestures backwards to the teaching of John XXIII and (especially) Paul VI, but the encyclical is also very much looking forward. He builds his foundation on the Christological anthropology of the Second Vatican Council's Apostolic Constitution Gaudium et Spes, and looks at the issues of his day (and ours) in the light of the encyclical's first sentence: "The Redeemer of man, Jesus Christ, is the centre of the universe and history". This is still well worth reading and re-reading.