The best thing about this very simple book was the title, which was a healthy reminder to me that there is no set of techniques out there that can guarantee that my children will turn out well. It can be very tempting for me personally to put undue emphasis upon formulas. However, when I do so, I am implicitly downplaying or even denying gospel truths! The way I parent certainly AFFECTS how my children turn out; however, 1) my kids are totally depraved, 2) they are responsible for their own actions, and 3) God is sovereign. These truths must drive me to prayer and to reliance on gospel grace! Also, if any of my children are walking with God, I should thank God rather than patting myself on the back or praising a particular methodology.
This book was also a helpful reminder to, in the words of Jay Adams, "always sharply distinguish God's commands from your suggestions." Many parenting methods or teachers have confused those two things.
One potential danger of this book is that it seems to lean toward the hyper grace position. Newheiser has co-authored a couple of books with Elyse Fitzpatrick, who I believe is a pretty strong proponent of hyper grace, and he quotes her a lot throughout the book. I was shocked that Newheiser also quotes Andrew Farley, a Christian pastor, blogger and radio talk show host who is blatantly hyper grace. (I wrote a blog article refuting a Farley post that denies that Christians need to confess their sins. Farley also denies that the "flesh" in Scripture is a living sin nature with which believers must reckon.)
Another critique of this book would be although Newheiser proves his point pretty well, he doesn't give much attention to what Christian parents SHOULD be doing. Perhaps that just wasn't his purpose in this book, but it certainly does limit the book's usefulness.