I see a pattern developing in the book. The author states that the present gospel seems to have a hole in it. The gospel seems to be more about alleviating poverty and fighting injustice rather than salvation in the work of Jesus Christ, and the church is not out fighting injustice or feeding the poor (or at minimum is blind to it).
So far, it seems, that the author is confusing the gospel for the fruit of the gospel. Let me offer a simile. If the gospel is like a fruit tree, it should grow up and produce fruit. The gospel is the tree and the outgrowth (or fruit) would be an others-centered life (including helping the oppressed and poor). Now the fruit is not the gospel, but only an outgrowth of it. We can offer people the fruit but it is not the tree. I think we could mistake "the root" for the "fruit."
I see a movement happening in our culture of "social justice" where churches and denominations are leaning toward replacing the salvation message of the gospel with social reform agendas. The "hole in the gospel" is actually the omission of the work of Jesus Christ on the cross--His Substitutionary Atonement. The "world" is out trying to fight injustice and poverty (and we should join them), but they ARE NOT preaching the good news of salvation in Christ. That is the church's job.
We must not be lured away from our primary call and substitute social justice for the gospel. To be honest it is much easier to be a part of a movement of social justice than it is to preach Christ crucified. 1 Corinthians 1:18 says,
For the message of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God.
People do not take too kindly to the gospel as they do to the fruit of the gospel. We must preach the gospel and give away its fruit, but we must guard against presenting social justice as the gospel.
I will be continuing to read the book and will update periodically, so my thoughts may meander a bit.