Jason Stellman's book Dual Citizens: Worship and Life Between the Already and the Not Yet made my Best of 2010 list. It's a great introduction to the concept of Christians dual citizenship - and its practical too! I disagree with him on a few things, but his overall premise and presentation are really good.
Just found these video introductions to the book. Check em out, and if you're interest is peaked (or ire raised), read the book.
We live simultaneously in this age and the age to come. The Holy Spirit is our engagement ring:
Worship is what we do when we gather as the church. It is holy. Life isn't holy, it's common. Both are done for the glory of God: