Kelly's work is definitely a standard in the arena of historical theology. In fact, Kelly himself is considered one of the foremost authorities on Patristic Church history from the 20th century. That being the case, it goes without saying that this work is highly respected and thus a standard in its field. Nonetheless, the text is written in such a way that almost anyone who puts forth an effort to read it can understand it. Kelly has a style of writing that brings the reader into the book without actually confusing the reader in unexplained detail and jargon.
This text is divided into four parts. Each part covers pertinent topics and issues from certain time frames in Patristic Church history. For instance, part two covers the Pre-Nicene theology regarding the Trinity, Christology, Redemption, and Ecclesiology. Each part is broken down in a similar fashion thus working through the Patristic period from the First Century of the Church to Augustine and the fifth century (early medieval period).
All the major doctrines, theologians, apologists, creeds, and councils are covered in some sort or fashion. Moreover, Kelly provides a wonderful Prolegomena (which is part one) to introduce the time frame, setting, background, etc. which leads up the continued formation of the Christian Church.
The wonderful thing about this book is the wide audience it commands. Both theologians and historians will benefit from its pages. Moreover, lay people who are simply trying to gain a better understanding of their heritage and doctrine will find helpful information and facts well organized and easy to follow. Some of the major doctrinal issues in this text include The Trinity, salvation/redemption, original sin, grace and forgiveness, the sacraments, Mariology, and the authority of the Bible.
Other helpful features of this text include an extensive bibliography, the revised edition includes a new chapter on Mary and certain saints, exhaustive references and footnotes, and a very detailed index. This text is an absolute must for those who are studying Church history as well as theology, and for anyone who simply wishes to gain a better understanding of Christianity. I highly recommend this book!