Its a bit meta and hard to swallow for a geek like me, but somehow I actually get what he's saying.
I believe the point that Brooks is trying to make is that the package and the content come together as one to convey the message as the author intended to convey it.
I have a few places that I write and I've been going through the process of putting a lot of thought into redesigning them to better match the tone and feel that I want each place to convey. Part of that process is making sure the content is clear and easy to read. The sidebar elements are not overly distracting, yet they do not disappear, etc.
Its interesting to read the same thing I wrote in different themes as it does seem to feel different for some inexplicable reason.