The book The Liturgical Books by Lancelot C. Sheppard is a comprehensive historical survey of the liturgical books of the Roman Catholic Church and their development from their origins to their officially accepted form in the mid-20th century. This book, part of the Twentieth Century Encyclopedia of Catholicism series, traces the history of the books that guide the prayers and official celebrations of the Catholic Church. Sheppard explains how the liturgy, as the prayer and praise of God by His people, must conform to Church law and has therefore undergone many reforms over the centuries. In short, this book is a historical guide focusing on the evolution and significance of the practical books used in Catholic liturgical celebrations, emphasizing how changes in these books reflect and facilitate the development of the faithful's participation.