I just finished reading this book on expository preaching by Bryan Chapell. The majority of the book is on the nuts and bolts of preparing an expository sermon. It's good, but not anything amazing. I still think Wayne McDill's 12 Essential Skill for Great Preaching is the best book on the mechanics of preaching that I've read. But there were 2 chapters in Chapell's book that were outstanding; they alone made the book worth buying.
In chapter 2 he describes what he calls the fallen condition focus (FCF) that exists in every text. It is "the mutual human condition that contemporary believers share with those to or about whom the text was written that requires the grace of the passage for God's people to glorify and enjoy him." The FCF is the purpose of the text and thus the purpose of an expository sermon. Finding the FCF points the preacher to the reality that biblical solutions to our problems must be divine and not merely human.
Chapter 10 is the heart of his book. "Christ-centered preaching rightly understood does not seek to discover where Christ is mentioned in every text but to disclose where every text stands in relation to Christ...Each text manifests God's grace in order to prepare and enable his people to embrace the hope provided by Christ." As Jesus described on the road to Emmaus, all texts point to him; our preaching must reflect this reality. It's the only way to ensure grace is the solution offerred for problems, not our works. Chapell offers some very practical steps for helping to identify how a text stands in relation to Christ.
This redemptive approach to preaching has been very helpful in my lesson preparation time. I think every preacher and teacher should read these 2 chapters.