One of my favorite encyclicals, both for its content and eloquence, is John Paul II's Redemptor Hominis. It is a masterful overview of the meaning of Christ and (re)reading it is a wonderful way to enter into the celebration of Christmas. Here is a favorite passage:
Man cannot live without love. He remains a being that is incomprehensible for himself, his life is senseless, if love is not revealed to him, if he does not encounter love, if he does not experience it and make it his own, if he does not participate intimately in it. This, as has already been said, is why Christ the Redeemer 'fully reveals man to himself'. If we may use the expression, this is the human dimension of the mystery of the Redemption. In this dimension man finds again the greatness, dignity and value that belong to his humanity. In the mystery of the Redemption man becomes newly 'expressed' and, in a way, is newly created. He is newly created! . . . The man who wishes to understand himself thoroughly--and not just in accordance with immediate, partial, often superifical, and even illusory standards and measures of his being--he must with his unrest, uncertainty and even his weakness and sinfulness, with his life and death, draw near to Christ.
I also like the encyclical's articulation of the Church's mission, an articulation that is broad and ennobling and which needs repeating today: "The Church's fundamental function in every age and particularly in ours is to direct man's gaze, to point the awareness and experience of the whole of humanity towards the mystery of God, to help all men to be familiar with the profundity of the Redemption taking place in Christ Jesus."
Click here to read it in full.