The book "History of the Christian Orthodox Church" is a reference and textbook on the course of church history from the first centuries of Christianity to the beginning of the 20th century. As its author, Archpriest Pyotr Smirnov, notes, church history only at the beginning of its narratives uses information from the sacred books of the Old and New Testaments, and only then draws information from records and evidence of general historical origin and significance.