Volume Three of this translation of the Rationale Divinorum Officiorum contains Book Four of this work. Here, over fifty-nine chapters, the Mass and all which occurs during it is examined in great detail. Following an introduction it begins with the vesting of the priest and ends with the final blessing. Throughout the entire work the reader discovers that Durandus is not superfluous with words. Each paragraph is tightly compiled and filled with much to reflect on. This book is likely to be not only the most detailed examination of the Mass which has ever been written but also one which speaks of the various levels of spiritual expression it contains. This book can prove fruitful to anyone who wishes to enrich their spiritual experience of the Mass. The translator of this work, Janet Gentles, has spent over forty years exploring the spiritual foundations of both Christianity and Judaism as both assist in gaining an understanding of the profound teachings of the Bible. Her publication the Rationale Divinorum Officiorum, provides a substantial contribution to such understanding.