If I had to recommend one chapter, it would be Tim Keller's. In the introduction to the book I summarized Keller's chapter in this way:
Tim Keller suggests that our current cultural situation poses a crisis for the way evangelicals have been doing evangelism for the past 150 years, causing us to raise crucial questions like: How do we do evangelism today? How do we get the gospel across in a postmodern world?
Keller believes that we need to rethink our ordinary way of doing ministry due to the cultural changes (especially in secularized Europe and places in the U.S. that are similar) and the fact that the church is now on a mission field.
He proposes six ways that the church has to change, finding parallels of Jonah and his mission to the great pagan metropolis of Nineveh. Keller calls these six factors: (1) gospel theologizing (all of theology must be an exposition of the gospel); (2) gospel realizing (we can “know” the gospel and yet not truly know the gospel); (3) gospel urbanizing (many Christians must move to the city, urbanize the gospel, and create strong versions of gospel communities); (4) gospel communication (through evangelism that is intelligible, credible, plausible, thorough, progressive, and process-oriented); (5) gospel humiliation (Christ’s power is evident through your weakness); and (6) gospel incarnation (within a pagan city God’s people are to be neither withdrawn nor assimilated, but rather distinct and engaged). In conclusion, Keller asks if we might be insulting God with our small ambitions and low expectations for evangelism today.