Both volumes of “Orthodoxy” by Metropolitan Hilarion (Alfeev). The book will tell in detail, thoroughly and systematically about the history, canonical structure, doctrine, temple and icon, worship, church music of Orthodoxy. Metropolitan Hilarion (Alfeev) in the preface to “Orthodoxy” writes: “The main idea of this work is to present the Orthodox Christianity as an integral theological, liturgical and worldview system. In this system, all elements are interconnected: theology is based on liturgical experience, the main characteristics of church art, including icons, singing, and church architecture, flow from liturgy and theology. Theology and worship influence ascetic practice, the personal piety of each individual Christian. They influence the formation of the moral and social teaching of the Church, its dogmatic teaching and canonical structure, its liturgical system and social doctrine. Therefore, an appeal to history, to the origins will be one of the leitmotifs of this book.” About the intended reader of his book, Metropolitan Hilarion writes: “A feature of this work and its difference from the above-mentioned introductory books is the desire for a sufficiently detailed and voluminous presentation of the material. The addressee of the book is a reader who has already become familiar with the “basics” of Orthodoxy and wants to deepen his knowledge, and most importantly, bring it into a system. The book is characterized by a leisurely rhythm of the narrative, requiring patient and thoughtful reading."