Thanks for the kind words about the book! The topic of branding deployment is such a massively wide and deep one -- in the book we decided to stick to the decision points along the way. I debated getting more specific with some examples but worried the chapter would end up being 100 pages
The question you ask is a great one though. Fortunately, this topic was covered on MSDN in a great little whitepaper. In general, you don't need to worry about setting the CSS like in the example. The preferred way to do that is to reference the CSS in your master page -- but there are some instances where it can be useful so it is worth seeing in the example. But I normally remove that part. Take a look though and hopefully this will do the trick!
SharePoint Server MVP | Sr. Consultant SharePoint911