In Mission-Critical Security Planner, Greenberg lays out all the security elements that should concern you and what questions you should ask about them. With this book, half the battle is won because you at least know how to do the planning. You still have to do the planning, but with the worksheets and tips provided in the book, that will be much easier than it used to be.
I read the book twice: once to get an idea of what all the worksheets were about and once to really read them with all the technical and practical details provided by Greenberg.
Greenberg identifies 28 security elements, including 15 fundamental elements, (six of which are core elements), and 13 wrap-up elements. Core elements include things like authorization and access control, authentication, encryption, integrity, nonrepudiation, and privacy. Those may seem obvious, but Greenberg has a lot of useful things to say about them that others haven't said.
Perhaps the most valuable part of the book is all the other elements, which we tend to forget, including addressing and routing (with tips on how to get those right from a security point of view), configuration management, directory services, time services, staff management, legal issues, and so on.
I'd be interested to see some projects get implemented with Greenberg's methods. I think it should work quite well, although due to entropy, laziness, over-worked engineers, and other such factors, I would guess that some of the numerous worksheets will fall by the wayside. But I think Greenberg would be OK with that as long as most of the worksheets are maintained and the company adopts security as a way of thinking.
In summary, this book is definitely worth reading, probably numerous times!