Interesting premise. "Saving Casper" is a follow up to the book "Jim & Casper Go to Church" (which I had not read prior to reading this; it is now on it's way to me. If you have not read the first one, I would suggest doing so before picking up this book; I think your understanding and experience would be a little more enriched that way!)
Jim Henderson is a former pastor, and Matt Casper is "currently" an atheist. They embarked on a journey to visit a number of churches, with Jim asking Casper questions and engaging in dialogue about his observations and thoughts on things that could be improved. This follow up book discusses their next steps as well as further reflection on that experience. The format is a back and forth conversation of sorts between the two (the book uses different fonts for each writer to help you more easily discern who is saying what) and no matter what you think about religion or atheism, it is certainly interesting. What I took as the overarching point was that we should be willing to engage in dialogue and then LISTEN, be open to hearing other perspectives, and be respectful of other's beliefs, even if they are not your own. Relationships will change everything.