This remains a timely book. Zahl incisively criticizes the almost universal tendency among scholars to leave Christ within the confines of his Jewish context. While Christ was a Jewish man in Palestine during the Second Temple Period, orthodox Christianity upholds him as the God-Man, a universal figure (for more on the scandal of particularly, check out E.L. Mascall's work). Zahl's project, then, is to show that Christianity proper really begins with Christ himself, not with Paul, Constantine, or later innovations. Jesus' own life and teachings, while flowing from his Jewish setting, were disjunctive. We don't need a Christianity that looks more Jewish, we need a Christianity that looks more like Christ.
There were a few places where Reformed theology figured too much in the argument where it could have been muted for a better "Mere Christian" approach. But, this is Paul Zahl so it can be overlooked and is even endearing at times.
I found this book particularly helpful as a pastor. Zahl present important critiques of academic trends like the New Perspective on Paul and Historical Jesus studies. I have seen a number of people drawn not only to these fads but also to harder "Jewish roots" style heresies which need to be corrected. After reading Zahl's work, I feel better equipped for situations where I may need speak orthodox Christianity to folks who have been misled in this regard.