This book is a comprehensive guide to the sacred liturgy, featuring the texts of two influential encyclicals, "Mediator Dei" and "Sacrosanctum Concilium", alongside insightful commentary from Aiden Nichols. These foundational documents on liturgical reform provide a framework for understanding the importance of preserving the sacred traditions of the Church while also adapting to the needs of the modern world. Nichols' succinct commentary provides a valuable context and explanation for these crucial texts, offering readers a deeper understanding of the principles and practices that underpin the sacred liturgy.