The opening to the synopsis on Goodreads is "Author... Timothy Keller with his most provocative and illuminating message yet."
Maybe it's just me and the church I attend... but I didn't find this message to be provocative or illuminating. Not that's it's a bad message or anything... but none of it felt "new" or illuminating to me. In fact, the book itself felt a tad repetitive.
An upside: this book would be good to hand to someone who thinks that all Christians are uber Conservatives who hate all charity. Just because someone is politically Conservative and doesn't support welfare for everyone indefinitely doesn't mean that they think charity is bad; just that it should be discerning.
Another upside: this book has all the Biblical proofs that justice is good and should be pursued, in case you ever needed to make this argument. All the Christians that I interact with on the regular are already doing lots of justice and/or charity in the world though, so I'm confused as to why this argument needed to be explored. Maybe things are different in NY, NY (where Tim Keller preaches).
The best upside: It's repeated a few times throughout the book that we (Christians) shouldn't perform justice because we pity someone in a harder situation than our own; we should perform justice because God provided justice to us when He allowed Christ to be put on the cross.
Tim Keller's writing is pretty great. The book is definitely accessible to all, even if you don't have a theological degree, which is great. It kind of read like transcripts of sermons. I would definitely consider picking up another Tim Keller book in the future.