Hey,
The book is definitely not targetted at absolute beginners, but I would say that if you are past this level, there is a lot that you can learn from it — especially if you don't have experience working on larger projects. Maybe in the future this is the kind of project you'd like to be prepared to work on?
When working on smaller projects, there are a lot of things we can do that we can't when working on larger ones. There are a lot more visitors at stake, more bandwidth costs, etc. Even if you don't apply everything we mention on the book, some of the tips on how to write CSS more effectively can still be applied to smaller sites.
Thanks.