D’Avril, who was Ancien Agent and Consul Général de France en Orient, in the first part of the book covers the origin of “Nestorianism,” the foundation of the Church of the East, the history of the Church of the East patriarchate up to d’Avril’s time, the organization of the Church of the East, their beliefs and customs, their missionary activity (especially with respect to Soqotra), the Church of the East in China and “Tartarie,” their relationship to the Greek churches, Protestant missions in the region, and finally the history of the Church of the East around Kurdistan. In the second part, he looks at relationships between the Church of the East and the Roman church, members of the Church of the East in Jerusalem, the uniate Chaldean church, the Christians of St. Thomas in India, and the Lazarist and Dominican missions. Finally, the third part consists of four appendices, one of which is a list of the Chaldean publications of Paul Bedjan. Any reader interested in Eastern Christianity will find this a valuable resource.