Having read the whole book, I personally found that I was sharpened regarding each of the key doctrines discussed in it. Indeed this is the main aim of this book. Each chapter does indeed "Engage with Keller", but each chapter goes beyond Keller, and rightly so. Each chapter seeks to engage the reader, to test his/her assumptions on each doctrine discussed.
One of my favourite chapters in this book is chapter 5 by Richard Holst which is called "Timothy Keller's Hermeneutic: an example for the church to follow?". Why do I like this chapter so much? It is because Holst contends for the use of good sense in handling Scripture, something which is not as common as we think, and that can also include some within a reformed circle. Of great value is Holst's explanation of the "Westminster Hermeneutic" on pages 173-176 and this is well worth reading, especially by preachers and elders. There are several principles that are illuminated for us.
The Principle of Principles: "the infallible rule of interpretation of Scripture is the Scripture itself (WCF 1:9)".
Principle 2: The analogy of Scripture, where "all things in Scripture are not alike plain in themselves, nor alike clear unto all (WCF 1:7) ... then such things should "be searched and known by other places that speak more clearly (WCF 1:9)".
Principle 3: The analogy of faith (the rule of faith) is not based upon private interpretations but it should be built upon sound exegesis. WCF 1:10 summarises this idea: "The supreme judge by which all controversies of religion are to be determined, and all decrees of councils, opinions of ancient writers, doctrines of men, and private spirits, are to be examined; and in whose sentence we are to rest; can be no other but the Holy Spirit speaking in the Scripture".
Therefore, our exegesis is not done in a vacuum, because we have so many faithful exegetes who have gone before us and these should be consulted to help us safeguard the church from speculations or the introduction of new and novel doctrines.
Holst writes in his conclusion that "expounding and applying Scripture is a huge, sometimes crushing, responsibility" (p 190). This should be the attitude of every minister of the Word. I hope that you enjoy this chapter and remember two Biblical proverbs in doing so.
Iron sharpens iron, and one man sharpens another (27:17).
Good sense is a fountain of life to him who has it, but the instruction of fools is folly (16:22).