One way to judge the popularity and effectiveness of a publication is to see how many editions have been printed.
It would appear "The Power of Vision" by George Barna is very popular and very effective.
It may be that although most pastors and church workers want to do ministry with a clear vision of God's plan, that vision is elusive. Barna defines vision, teaches the reader how not to confuse vision with mission, ways that a ministry can prosper by having a well defined ministry, and providing materials which can help any ministry or church group define and implement a statement of vision.
Concerned that the ministry you lead is without a clear vision. A good start to changing is to grab a copy of "The Power of Vision."
