This book is written in response to John Piper’s book “The Future of Justification”, which I have not yet read. You do not have to read Piper’s book in order to understand or enjoy Wright’s book.
The whole debate is about the “New Perspective of Paul”, a debate I do not fully understand, although this book helps a lot. From what I can gather, the arguments center around what Paul was really talking about when he was describing salvation in terms of God’s faithfulness and righteousness. The Old Perspective focuses on the individual’s salvation and little else, while the New Perspective says there is more going on than that: a greater purpose which looks at the overarching salvation plan of God including Old Testament Israel.
It seems like it is an “either/or” argument when it should be “both/and”. God both saves the individual sinner through the work of Christ and is creating a special people for Himself who will one day inherit the new heavens and the new earth.
I do recommend the book.
Here’s a video of N.T. Wright explaining the book himself…