In the introduction, he suggests skimming through the text once and then dipping further into the sections that are of most interest to any given reader, and I agree that this is a great approach to the book. While I enjoyed, say, the chapter on memoir writing, I'm less likely to go back and think about that in detail than perhaps the chapters on beginnings and on revision. But others will feel differently depending on what they're writing and what stages of their projects they're struggling with.
I actually found the two chapters on revision particularly helpful. I'm not aware of any (or at least many) other craft books that break down the different stages of revision so comprehensively. Koch talks about what aspects of the writing (plot, structure, characterization, logic etc) one might focus on in an early revision versus a later revision. He also talks about the tricky question of when to bring in outside readers, who to bring in, and how best to present a draft manuscript to an outside reader.
If you're interested in writing something yourself, or even if you're interested in the writing process for it's own sake, this is a really engaging read. I know I'm going to go back to it repeatedly having enjoyed it the first time through.