The reason books are so important, in my estimation, has to do with their ability to radically expand our horizons and help us think outside the box. Left to our own devices, we all can be somewhat parochial. Books, especially books written by people far afield of our own perspective, can quickly disabuse us of our sense that the church is only and always as we currently experience it. Church is much more wild and wooly than that.
So here is a somewhat random and disorganized list of the books that have influenced my own thinking the most re: mission development. Often the titles will tell you what you need to know, and the links, all to Amazon, can lead you to summaries and reader comments. I've written a few reviews on Amazon of some of these volumes:
Evangelizing Church This is the definitive Lutheran volume.
The Forgotten Ways: Reactivating the Missional Church This is one of those books that will blow your mind. I needed to read it three times to really let it sink in, and it still hasn't.
Unbinding the Gospel: Real Life Evangelism, 2nd Edition One of the most winning writers I've ever encountered.
Organic Church: Growing Faith Where Life Happens This guy is brave and amazing.
Transforming Discipleship: Making Disciples a Few at a Time A great model for thinking small through multiplication, and going deep in discipleship.
Missional Renaissance: Changing the Scorecard for the Church (Jossey-Bass Leadership Network Series)
The Missional Leader: Equipping Your Church to Reach a Changing World (Jossey-Bass Leadership Network Series)
The Mission of God: Unlocking the Bible's Grand Narrative This is the big picture bible resource for thinking about God and mission.
Paul the Missionary: Realities, Strategies and Methods And similar, but on Paul.
Viral Churches: Helping Church Planters Become Movement Makers (Jossey-Bass Leadership Network Series)
The Monkey and the Fish: Liquid Leadership for a Third-Culture Church (Leadership Network Innovation Series)
Makers This one is a sci-fi novel, just a disclaimer.