This is just a confused book. On the one hand, I strongly agree with a lot of Wilson's diagnoses of ills in the modern American church, such as individualism, ignorance of the Old Testament, tendency toward dualism, and so forth. However, I disagree with what he deems to be the cause of it: the church's de-Judaization, or as he puts it, cutting itself off from its Hebraic roots. Wilson's solution is for the church to return to its Jewish roots and once again be nourished by the root.
The biggest problem with the book is its exegesis of Romans 11 and the inconsistent way Wilson identifies "the root." Taken as a whole, Wilson defines "the root" basically as Judaism as a whole, including its present form. At one point, he even essentially defines the nourishment of the root as the study of the Hebrew language. He recounts how Harvard once had a thriving Hebrew studies program, but now that the curriculum has changed, "No longer do today's students have the opportunity or feel the need to partake of that reviving sap of the olive tree in the same way as Monis and his learners did" (p. 130). It's a confused interpretation and application. Nor does it taken into account what it means that some branches were broken off.
I was often left wondering who this book was written for. I feel like it's aimed at conservative Christians, but then the emphasis on the Jewishness of Jesus and the apostles seems just preaching to the choir; I don't know anyone who is orthodox who needs convincing of that. Part of me feels like he was responding to the quest for the "historical Jesus" at the time which devalued his Jewishness, but that crowd is not the audience for this book.
Chapter 9 was just bad linguistics. Overly psychologizing the Hebrew mind based upon the grammatical structure of the language. Early on, he also tried to interact with James Barr's The Semantics of Biblical Language, but I don't think he understood Barr all that well.
Ultimately, I'm not entirely sure how this is a Christian book. Wilson largely finds little of value in the Christian tradition and very much of value in the Jewish tradition. Wilson thinks the Church went wrong long ago, back in the second century, and now needs to course correct by essentially becoming more Jewish. He even went so far as to essentially pin the Holocaust on the church's trajectory ("Perhaps the most important reason the Holocaust happened is that the Church had forgotten its Jewish roots" [p. 101]). Missing here is any distinctively Christian message of hope in Jesus as the Messiah or in his resurrection. I have a lot more I could say about the overall program, but suffice it to say that Wilson does not seem to view modern-day Jews who deny Jesus as Messiah as branches who need grafting back into the olive tree, but instead seems to consider them as the root that Christians need to be nourished by.