I really enjoyed this book, and I recommend it. If you pick it up, I recommend you read part one and three; skip the middle. The middle is rather laborious.
In this book, Webb is suggesting a matrix from within which we can work to discern what is culturally bound in Scripture and what transcends cultural context and is "universal". Of course all scriptural texts have a cultural context and are in that sense culturally bound, but what Webb is after are those texts which no longer offer us explicit, or at least highly explicit, application for our cultural context: for example, Old Testament passages on Levitical law or New Testament passages on slavery and women.
Webb challenges the various traditional reasons given for why we no longer explicitly apply certain texts to our lives. He suggests that interpreting the slavery passages for today's context by merely plugging in the modern workplace for the slavery variable is hermeneutically irresponsible. And while appropriate, in deed necessary as a modern day application, it cannot be an interpretation. We interpret what the writer intended, and we interpret what the passages mean beyond what the author himself knew; we interpret what it means per the intentions of the Holy Spirit. There is an underlying ethic, or principle ("trajectory of redemption") that is interpreted from the text. The text is pointing us in a particular direction, and if we follow the directions of the Apostle, we will abolish slavery. How else can a master "treat [his] slaves in the same way" as Paul has instructed slaves to treat their masters (Eph. 6): "providing them with what is right and fair" (Col. 4)? We realize that the slavery texts, for example, are pointing toward the abolition of slavery while simultaneously speaking into the cultural context of the time, meeting the culture where it's at.
As far as the "women" texts are concerned, we do choose to say certain texts are culturally bound and others are not, but the grounds for choosing which is which typically continue to ignore the redemptive movement of God and his word. SLH uses this hermeneutic of redemption to suggest that there is a similar movement in the "women" texts which breaks out of the explicit words of the text given in the cultural climate of the early church and points toward egalitarianism (or at least a "soft patriarchy").
From the principles of Webb's hermeneutical matrix, he does not see evidence for such a movement in regard to the issue of homosexuality as many are now calling for. And I think Webb's arguments for this are significantly weaker than his arguments on the "women issue"; he seems to take too much for granted.
I like this idea because it considers both the whole of Scripture as well as historical-cultural context in which it was written as important in the process of interpreting individual texts. I like it because I believe the idea of a trajectory of redemption jives with the way God works in the world and in our individual lives. I'm sure Webb's hermeneutic isn't flawless, but for the above reasons I don't think it can be ignored.