This book is written from a liberal Protestant perspective and leverages the historical-critical method of biblical interpretation to construct a New Testament theology. What distinguishes the author's method from others is the use of the Old Testament, not in typical Christian theological fashion, reading backwards the New into the Old Testament, but rather taking the position that the Old Testament was Scripture for the New Testament writers and reading forwards into the New. The book itself deals with four topics: Christology, soteriology, ecclesiology, and ethics (eschatology is mixed in to the soteriology an ethics sections).
This book will be tremendously dissatisfying to evangelicals and mainstream Catholics because it uses the historical-critical method, rather than constructing a New Testament theology from dogmatic theology backwards to a biblical theology. Dunn treats theology (using the term theologizing) as a historical process and locates the New Testament writers in historical context and the theologies of Second Temple Judaism and the factionalism of the time. But for the typical Anglican, liberal Catholic, or liberal Presbyterian it is an informative read and constructively rather than destructively deploys mainstream academic biblical scholarship. My one complaint is that stylistically Dunn too frequently deploys rhetorical questions. I would prefer a provocative statement rather than leaving a question in its place.