This book has all ready been splendidly reviewed, but I felt I may have a few things to note. The author is a professor, and the book is written as such. People seeking "warm fuzzies" from reading a book about rediscovering classical Christianity are not going to find it here. They will instead find a powerful look at the way that classical Christianity can be drawn upon to reenergize the church, specifically the evangelical church, and make it a more dynamic force in the world as the body of Christ. Very highly recommended.
I found this book exciting and easy to read. The reason is that Webber connects the ethic and doctrine of the ancient Church to the postmodern world. The situations are quite similar. Webber, a conservative Baptist turned evangelical Episcopalian, argues that the history of the Church consists of different paradigms. Each paradigm is a different expression of the faith, relevant for the time, but inadequate for later generations. Thus, while reformation theology of Sola Scriptura was necessary to counteract the excesses of the later Middle Ages, for the postmodern (and for the early) Church it doesn't work very well (it has led to 1000s of denominations). Webber has some very helpful tables comparing beliefs of different paradigms.
Webber correctly observes that postmodern people are more diverse, less concerned about minor doctrinal differences, and more symbolic. This coincides with new scientific theories that posit a dynamic, non-Newtonian universe. So how can we find authority and meaning? The answer is classical Christianity. Enlightenment rationalism doesn't work anymore, as relativity destroys any idea of objectivity, so theology must be done in the context of the Christian community, the Church, as it was in early Christianity. The Church provides the interpretive authority of the Bible through the creeds. However, this authority is broad, and is something that Catholics, Orthodox, and (most) Protestants share in common (see Vincent of Lerins' canon). As in the early Church, Jesus is the ultimate focal point of the Church, and apostolic tradition and the Bible point to him.
Webber makes use of the "Christus Victor" model of the Atonement. This is the predominant theory of the Atonement expounded by the early Church. This theory says that Jesus, in his Incarnation, death, resurrection, and teachings, conquered evil. It is holistic, rather than narrowing down "when" Christ saved us, such as at the Crucifixion. Thus there is room for unity and mystery in the doctrine, just as in the early Church.
Ultimately, as Modernity dies, Webber advocates a return to the early church of the Fathers. Thus the Church needs to be less individualistic, unified by the creeds, symbolic, sacramental, and arts oriented. However, Webber doesn't want postmodern values to *shape* the Church (e.g. when the Church is a business or side-show), but rather that the Church must be able to convey its basic truth in the postmodern world. Webber is simply advocating what many are already doing: rediscovering the riches of ancient Christianity, dismissed by many enlightenment-era Christians as "outdated" (liberals), or "irrelevant to faith" (fundamentalists). The era of Classical Christianity, when major doctrines were shaped, ethics were worked out, and the canon closed, is neither outdated nor irrelevant.