The book Worship in a New Key: What the Council Teaches about Liturgy by Gerard S. Sloyan examines the teachings and spirit of the Second Vatican Council regarding the liturgy of the Catholic Church. It explains the significant changes in the Catholic liturgy introduced after the Second Vatican Council (1962-1965). These changes were designed to make worship more accessible and understandable to the laity. One of the Council's primary focuses was to encourage the full, conscious, and active participation of all the faithful in liturgical celebrations. The book describes how this was implemented, for example, through the use of vernacular languages, more relevant preaching, and a greater role for the laity in church services. Overall, the book serves as a guide to understanding the Second Vatican Council's vision for the liturgy, and its relevance to the life and mission of the Church in the modern world.