While I don't agree with everything that Tim Keller says or writes, I do find him to be a refreshing voice. He is what I would call an intellectual evangelical, as opposed to those who express an overly simplistic form of evangelical Christianity.
His book, the Prodigal God, is one of the cleanest explanantions of Jesus parable of the Prodigal Son.
In this short video above, he makes a claim that people are seeking out transcendence in the midst of an increasingly secular culture. Note though, the difference. People are seeking gospel, wherever they find it. If they don't find it in a church, they are not going to stay.
In my mind the two fundamental searches in our time are a hunger for authentic community and a hunger for an encounter with God. I have termed this elsewhere as, people don't want to know if the Christian faith is true, they want to know if it works. I have even suggested that Lutherans are still answering a 16th century question with a 16th century answer. Are we worshipping the reformation? My thought is that we need to be answering a 21st century question with a 1st century answer. Tim Keller helps answer that question, especially in the Prodigal God.