Metaxas has said he sees Bonhoeffer as particularly relevant for our time, in part because he sees parallels between contemporary America and Germany between the wars. One reviewer I read of the book claims that Metaxas wishes to present a Bonhoeffer that can be or is on the side of the Religious Right culture warriors. I think both Metaxas and Metaxas' critic are missing something.
One of the things that the reviewer pointed out was that Metaxas deemphasizes aspects of Bonhoeffer's times at Union and emphasizes his experience with the Abysinian Church in Harlem in such away as to paint Bonhoeffer as being on the Evangelical side of the curent culture wars. I think this critism could have some weight except that Metaxas is insistant that Bonhoeffer comes from and is other than American Christianity (liberal or conservative). This has long been my sense of Bonhoeffer. I first read his Discipleship (under the English Title of Cost of Discipleship) in a moderate evangelical context, the spin that was attempted didn't fit my reading of the text. Then I encountered liberal scholars who sought to build whole positions out of his musings about "religionless Christianity" and claim Bonhoeffer's authority for what they spun out of that musing. As I am reading Metaxas it seems to me that Bonhoeffer's convictions don't make alot of sense unless we step back and recognize that we can't use Bonhoeffer for our theological and ideological ends.
My thoughts in part are at the moment around the Church Struggle after the Nazis gained ascendency, and Hitler ruled Germany. In seminary I read various books and accounts of it, and I found it difficult to grasp, and even Metaxas in attempting to give an account through Dietirch Bonhoeffer's life leaves a great puzzle. Its not the facts that aren't clear, but the responces to it from all players. Even the actions of Christians outside Germany is puzzling. Metaxas gives greater prominence to Bonhoefer's role in the Church Struggle than any other account I have read before. Bonhoeffer had a sense of the church that caused him to be frustrated both with the Confessing church and the ecumenical movement of his time. In some sense Bonhoeffer also stands out against his own time and theologies.
So far one of the more puzzling things about Metaxas' account that it doesn't explain but simply recounts Bonhoeffer's politicking to get the ecumenical movement to condemn the Reich German Evangelical Church and recognize as the only true representative of the church in Germany the Confessing Church Movement. Bonhoeffer does this while the leaders of the Confessing movement wanted the ecumenical recognition they were reluctant to become an "alternative" church to the church headed by the Reich Bishop. Why wasn't it enought for Bonhoefer for the Confessing Church movement to be a movement, or even why was it a travesty for the confessing church movement to be simply recognized as a church in Germany by Christians outside Germany and the ecumenical movement? From an American perspective you don't like what is going on in your church and you've tried to change it well its perfectly legitimate to start your own, and then you show up at ecumenical groups (if you are so inclined) as a new Christian church. One is left wondering why the agonizing over leaving an institution that was so clearly corupting the Gospel?
I think the above is difficult to unpack, there are unexamined assumptions underlying this for both Bonhoeffer and those of the Confessing Church. There is also the unexamined assumption for many American Christians I know that continuity has no role in the character of being the Body of Christ, and while from a Roman Catholic perspective those who went with Luther in the Reformation had not retained continuity with the church, it seems to me that in the Church Struggle both Bonhoeffer and the Confessing Church were struggling with a belief that contrary to Rome it was in fact the Evangelical (ie. Lutheran) church that had retained continuity. Also, there is indication that Bonhoeffer's sense of ecclesiology was other than that of the Confessing Church.
Lastly it is perhaps significant that Bonhoeffer's thought was formed in conflict and struggle. As such I think it is perhaps best to approach him as one whose theology can never be appropriated. Rather he stands as a challenge as he did to his contemporaries. Metaxas may be correct in having written and hagiography rather than a critical biography. Bonhoeffer stands and as a martyr challenges us with the impossibility of the Gospel and the church, and theirs simultaneous absolute claim upon us who name ourselves as Christians, followers of Christ. This disturbs me and wont let me alone, and I am disturbed by the ways we all want to tame and make this martyr of Christ become a martyr of our pet ideas and American philosophies and theologies.