The Catechism of the Catholic Church
It is divided into four parts. (1) The profession of faith, or what we believe as Catholics. We say the creed at mass; it is part of the rosary. The Catechism explains in great detail what every line of the creed means. (2) The celebration of the Christian mystery explains the mass and the seven sacraments of the Catholic faith. (3) Life in Christ, living the faith with Christian morality. It shows us how to apply the 10 Commandments to our life. (4) Christian prayer, God calls us to pray to him always, what does that really mean; and it explains the meaning of the Lord’s Prayer.
There are many books and talks on the Catechism, some cover it completely and others focus on certain topics. The USCCB came out with the United States Catholic Catechism for Adults a few years ago. The USCCB also has a Compendium of the Catechism of the Catholic Church; a concise book covering all of the essential and fundamental elements of the Catholic faith. Fr. John Corapi created The Teachings of Jesus Christ, a series of talks that he gave to the diocese of Sacramento back in the 1990’s outlining the Catechism. This series is run continuously on EWTN, an hour talk each day. And there are many others who have also created teaching aides using the Catechism.