Michael A. G. Haykin’s Giving Glory to the Consubstantial Trinity: An Essay on the Quintessence of the Christian Faith is a brief history of the doctrine of the Trinity as it developed from the last quarter of the second century to the Council of Constantinople in 381. The four chapters address the importance of the Trinity and why Christians should care about it; the defense of its truth by Irenaeus of Lyons and the need for Christian creeds; the work of Athanasius leading to the Nicene Creed’s affirmation of the full deity of both Christ and the Holy Spirit; and the fourth chapter presents the defense of the Spirit’s full divinity as worked out by Basil of Caesarea and Gregory of Nyssa in the pneumatomachian controversy. The ancient church can be an intimidating period of history for beginners. Consider some of the personal names of the era—Irenaeus, Tertullian, Polycarp, and Athanasius, none of which are names likely selected by English speakers for children today. Added to the intimidation factor are the Greek term “homoousios,” which means the same substance, and the similar word, “homoiousios” (note the “i” inserted between the double “o” seen in the first word), which means similar substance; both these words were important in the debate about the Trinity. Added to the substance issues are the “pneumatomachian” (spirit-fighters) controversy at the end of the fourth century that was resolved by affirmation of the full divinity of the Holy Spirit. The term “consubstantial,” in the book’s title, means of the same substance in relation to the persons of the Trinity. Yes, studying the early centuries of Christianity can be intimidating but Giving Glory provides a brief and beneficial guide for understanding the importance of doctrines clarified in the ancient church. Even though there are only about a hundred pages of text, the author has provided a good sized select bibliography and a chronology of people and events. If you are interested in the doctrine of the Trinity and want a scholarly but brief book, then Giving Glory to the Consubstantial Trinity by Free Grace Press will guide you through the key individuals and the complex issues concerning the Father, Son, and Holy Spirit.