One of the most significant book I have read on the church is Total Church by Tim Chester and Steve Timmis. It has helped shaped my thinking about how the Gospel functions as the center of the church. It truly is an important book by two men who are not only theologians but church planters as well (what a great combination!). The COS staff is currently reading Total Church together.
Mike McKinley who pastors in Virginia and blogs over at Church Matters has posted three interviews with Steve Timmis. I encourage you to read the interviews and the book. Incidentally, Mike grew up at Church of the Saviour.