Abstract atonement theory vs actual history
The fundamental question sitting in the background throughout Brondos' book is "how does Paul's view of atonement compare to the historical facts of Jesus' life and death?"
Jesus was a person, who lived at a particular time in history and did various things during his life. He gathered disciples, taught, healed, got into conflicts over the Law, the Temple and money. He got plotted against and killed by the authorities. Then God raised him from the dead. That's the story recorded in the gospels. That's the story his followers passed on to each other, its a story of Jesus' life and death and resurrection that purports to a historical account of something that really happened.
Now, if we heard this story as told to us by an early follower of Jesus, or read the gospels that recorded this story, the very first thing we would not say upon hearing the facts of the story is "so Satan's power over humanity is now broken" or "So thorough becoming human Jesus united humanity with God" or "so in dying Jesus took upon himself the sins of the world?". None of these ideas flow naturally out of the story. If you'd just heard the story of Jesus' life you wouldn't, from that story, deduce these ideas.
A view that was quite popular among scholars about a hundred years ago was the viewpoint that most of Jesus' immediate followers simply repeated the bare facts about his life, teachings, death and resurrection. It was believed they taught the historical story about Jesus, and then Paul came along and he wasn't interested in the historical Jesus as a real-person at all. To Paul (according to these scholars) Jesus was the Cosmic Redeemer, and Paul invented an abstract system of atonement in which Jesus' death is an event of cosmic atonement which is dissimilar from any other human deaths in history and which changes the very nature of reality itself. This was thought to have made Pauline Christianity far more attractive to the gentiles who were into religions that said this sort of thing. So it was thought Paul had invented these ideas basically out of whole cloth as he religiousifed
Christianity and brought it to the gentiles. In this way a huge chasm exists between the real Jesus of history which most of Jesus' immediate followers understood Jesus as and the non-historical cosmic Jesus of faith that Paul holds to.
Brondos is concerned about views such as this, where the views ascribed to Paul are either explicitly or implicitly divorced from the facts of Jesus' life and death. ie. where the "theory of atonement" is not obvious upon hearing a simple account of Jesus' ministry, where it involves hidden cosmic transactions that one has to be told about separately. Brondos sees numerous problems with this. He doesn't buy the idea that Paul is disinterested in the historical Jesus, and points to recent scholarship that has found numerous references to the life and teachings of Jesus throughout Paul's letters. He points out that in Romans, Paul is writing to a church he has never been to and yet uses Paul's normal atonement language with the assumption its recipients would understand it fine, indicating that Paul expected people who had heard the simple historical story about the life of Jesus would understand his atonement language and understand him to be saying essentially the same thing as what they already believed.
Brondos argues that a hypothesis that sees Paul's language situated in essentially the same narrative as the gospels actually does make sense of what Paul says. If one takes the view that Paul sees the atonement not as a single event of cosmic redemption accomplished once for all in a single act, but as an ongoing story, then one finds that this coheres very well with things Paul says. In a lengthy analysis of Paul's atonement language, Brondos concludes that Paul's story is the same story as the four gospels. Paul is not meaning to affirm a mysterious cosmic atoning event of a non-historical Christ, but rather to affirm the gospel stories of a historical Jesus whose life, death and resurrection form a unique part in the continuing global story of God's redemption.