The advice Frey gives that I'll take away and put to use immediately is his idea to give the overall thrust of the book, as well as each main character, a premise describing their plot or character development arc. For instance, the premise for Michael in the Godfather is that family loyalty leads to a life of crime, or for Scrooge in A Christmas Carol, forced self-examination leads to generosity.
I'm sure I've heard advice along these lines given before, probably in the form of "give each character a motivation," but that never seemed to work for me. People's motivations change moment to moment based on the situation. But phrased as Frey put it makes the idea a little more abstract, and its utility was immediately apparent to me: you can instantly tell whether a scene you're writing is relevant or not. Does the scene advance the overall premise of the book, or of the character(s) in the scene? If not, then it doesn't need to be in there. I do this already, of course, but the premise concept provides a way to screen each scene more quickly.
The worst advice I found was Frey's admonition to put together something called a "step-sheet" before you ever start writing. As he describes it, this is basically a detailed outline showing the dramatic rise and fall in tension throughout the book, and apparently it should take about a month to finish. For some writers that might be great, but I'm never going to do it. In my mind, anything more than a one or two page sketch at the beginning is a straitjacket. Start off with great characters and let them figure out how to navigate the plot.
Another thing Frey mentioned that I doubt I'll ever do, although it sounds intriguing, is to interview your characters before starting the book. This actually sounds like it might be a good way to establish their voice. Of course, my preferred way to establish a character's voice is to write the book and let it come out naturally. But who knows? Maybe if I'm having trouble with a character some time I'll give it a try and see if it helps.
One thing I appreciated about Damn Good is that it's more on the practical end than the cheerleading end of writing how-to books. Even if you don't agree with a suggestion, at least he makes one on nearly every page and you can take it or leave it. I've had it with the cheerleaders. I've written enough and gotten good enough I don't need the encouragement, and I'd rather read something with a high density of advice. For those who are looking for encouragement, turn to Bird by Bird, which is clearly the best in that category.
So as a writer, should you read this? Of course. If you want to write a novel, you should probably read a dozen of these. Half of what's in any of them you'll already know, and another third will be absolutely wrong for you, but that remaining fifteen percent is what you're after. I found my fifteen percent in this book and my guess is you will too.