The Book of CSS3 is an informative text for those who have a little CSS experience and would like to see what all the fuss is about with CSS3. However, if you have no knowledge of CSS you are going to be lost at sea while reading the text. It is certainly not meant to teach the basics of CSS, rather, as the title suggests it is more focussed on what is changing and being added in CSS3.
The book can be a little dry at times, but that is to be expected given the topic; this may be my bias here but CSS is much less interesting than Objective - C or some other programming language; yeah I know that is comparing two very different things and the CSS is not a programming language at all. I don’t think that the book should be passed up due to dryness, however.
You will learn a lot about the great and powerful new features coming with CSS3 by reading The Book of CSS3 and the book will serve as a great reference no matter how infrequently you may use the technology; I know it has for me.