This entire book is about how the church is supposed to be building itself up. The evangelism happens because non-church attenders would find church-goers so attractive.
In other words, don't do Kindness Outreach, don't do big Easter events meant to attract people. Simply encourage one another and allow people to become like you.
This is quite different than what you're hearing from some of the "superstar" church authors out there. Almost every book I've read on church growth/health deals with doing what you can to attract non-Christians. Peterson says that would happen naturally if your church people are healthy in how they treat one another and how they sincerely worship God alone during their Sunday morning services.
It's an interesting, divergent, and maybe arguably a biblical argument. I just don't feel like it would be something I would throw out there.
If you hate what the church growth people are claiming, you'll flock and promote this book like crazy as it's completely opposite.
This book was provided for review, at no cost, by P&R Publishing.