In response in part I am reading Moule's Birth of the New Testament.
The following is a quote from his introduction:
"evangelism is absolutely inseparable from the life of the Church (when it is alive) . . . . The initial kerygma or proclamation was spoken: when it came to be expanded into a written Gospel, it seems to have become explanatory rather than (primarily) evangelistic. If there are exceptions, these are perhaps the Gospels of Luke and John, which were possibly meant for non-Christian readers."