Ruth Langer's meticulously researched volume fills a gap in the study of Jewish liturgy. While many histories of the liturgy focus on the origins, use of language, and literary aspects of the texts, Langer's study provides an analysis of some of the dynamics that shaped the halakhot dealing with prayer, thus impacting directly upon the spiritual life of Jews. How did the legal system that discussed issues regarding the liturgy develop? What questions were asked, and around which factors did disputes come about? What concepts and practices contributed to the resolution of differences? As Langer notes in her preface, a significant force in the formation of rabbinic prayer and the legal system undergirding it was the principle of worship as an evolving phenomenon. Once prayer is understood as both a communal and an individual response to God's covenant with Israel, the intricacies of the liturgical system must be developed and justified. They must express the history of the community as well as the existential needs of the person of faith.