This book is growing popular of late, being touted as a solution to dying churches. The essence: Simple is better; streamline, and your church will do better.
The way to do this isn't very controversial on the surface: Keep yourself down to one central mission statement; make sure everyone on the church is on the same page with that statement; slaughter any sacred cow, or anything else, that doesn't fit the mission, and so on.
Mostly, this seems on target. However, the cynic in me sees some serious potential for abuse. The attitude of too many pastors and leaders is that apologetics is a nuisance, not something helpful for spiritual growth. It would be all too easy for such leaders to use The Simple Church to create The Simple-Minded Church -- one that might indeed grow but would be a mile wide, an inch deep.
That's fine as long as the people are insulated. But what happens when Dan Brown writes again? I can envision pastors refusing to do anything about it, under the premise that it would be "adding a program" or a "special event" or that apologetics is "not simple" and so doesn't fit into the program. I'm not saying Rainer and Geiger would go along with such reasoning; what I am saying is that, based on experience with pastors, as they say in Star Wars: I have a bad feeling about this.
Rainer and Geiger would probably say that serious education and apologetics would work in nicely with their system, and I am sure it could; their model for small groups would be just fine. I just wish they could have been able to take the time to say so, because apologetics ministry is extremely precarious in many churches, and highly vulnerable to head-in-sand sort of pastors who will now have a rationalization to use the easy "no" that the authors recommend to program additions that are seen as "unnecessary". A simple church pastor already inclined to leave out apologetics will now be someone you can't even argue your case with, if the "simple church" method is taken to heart uncritically.
Let me emphasize again that I am not faulting these authors at all. What I am doing is more like sounding a warning call for potential abuses of the system. To that extent, this book is recommended for the sake of our awareness and caution.