One thing you might notice about the letter to the Ephesians right away is that, unlike Galatians and both of the letters to Corinth, Paul has almost nothing personal or specific to say to the church at Ephesus. That has led some people to speculate that this short letter really was not written to the Ephesians, but was a letter more generally circulated to all of the churches. It has led others to speculate that Paul did not actually write it, but instead one of his disciples. (It would not have been a terrible thing in those days to write a letter "in the name of" one of your teachers.)
So this letter doesn't have juicy details about the sins of the Ephesians, or greetings to individuals that we want to know more about, except Tychicuscxzgt (Darn.) But it does have (and you'll just have to trust me on this) those really really long sentences that Paul is famous for (you can tell this especially if you read the original Greek). I believe the first 15 verses of chapter one are one long sentences. It also have a wide, expansive vision of God's mission in Christ: at the end of time, God will bring all things together in Christ, things on heaven, and things on earth. ALL THINGS. This is one of the places where Christian universalists get their universal hope.
So Ephesians has this expansive vision of a God who is in the reconciliation business, and this is not just about reconciling individual souls with Jesus, but reconciling strangers and sojourners, Jews and Greeks, lions and lambs, all of creation. In Ephesians you get the impression that our individual salvation is just a teeny weeny part of a huge plan.
But teeny though we are, we are each a part of something huge: God's plans for the re-creation of the whole universe. The doxology at the end of chapter three gives glory to God for just this reason: because God is doing great things through us and in us, greater than we could even ask for or imagine.
Ephesians is, in a way, like Romans. It's a miniature theology, only six chapters long. But Ephesians has more a missionary flavor to it, which might be why, when I was a missionary, I sort of gravitated to Ephesians. In Romans, we have "peace through God." In Ephesians, we have the peace that reconciles us not only to God, but the peace that reconciles us to one another. "He is our peace, because he has broken down the wall of hostility that divides us."
So Ephesians is.... cosmic. But, at some point, even in this cosmic letter, Paul will get down to earth.