The Constitution on the Sacred Liturgy says "The Church earnestly desires that Christ's faithful, when present at this mystery of faith, should not be there as strangers or silent spectators. On the contrary, through a good understanding of the rites and prayers they should take part in the sacred action, conscious of what they are doing, with devotion and full collaboration." What is needed and what the author offers here is that "good understanding" of the meaning and value of the Mass. After examining its historical development, Professor Adam explains each part of the Mass as it is currently celebrated. He uses understandable terminology and a form of presentation designed to increase appreciation of the Mass among the faithful and to provide the knowledge and impetus to achieve this in family and group discussions, in catechetical instruction, and in preaching.