It is a pretty straight forward look into the 1st Century Christian view of politics, that is important because these Christians were taught directly by Jesus.
Several quotes from the book stand out to me: " Paul was willing to use his Roman citizenship to demand the protections of the judicial process due him, but he engaged in no lobbying on the public policy issues of the day"
Paul's " Letters to believers in such important cities of Corinth, Ephesus, and even Rome betrayed no interest in secular political squabbles"
Paul "commanded submission to government, but in none of his many letters did he ever detail even one policy for the local church to urge on public institutions"
"Though they believed they were obligated to honor the governing authorities, the early Christians did not believe in participating in political affairs"
These Christians clearly lived by Jesus command to pay back Caesar's things to Caesar, but God's things to God.
This is also part of what it meant when Jesus said his disciples were to be no part of the world, just as he is no part of the world.
James also hit on this point when he said that friendship with the world is enmity with God, whoever wants to be a friend of the world is constituting himself an enemy of God.