I generally turn to "Dummies" books when I have no knowledge of a subject, but need quick information. I like the books... Unlike most techies, I like the humor contained within. One thing about techno-dummie books is that they generally give you just enough information to get up and running... They're great starting points. However, you will not learn standarized methods, as proposed by the W3C, from this book. You'll learn about selectors, but things like the box model are not really explained as well as they should be.
THIS BOOK IS GEARED TOWARDS IE BROWSERS ONLY - as the author states several times throughout. In regards to marketing, MS owning 90% market share, it makes sense to teach from this angle. But to learn the full potential of the language I can't see the justification. Firefox, Opera, and Safari, already support alot of selctors from CSS Level 3, leaving the IE viewers a degraded or dimished view of pages created to standard. It's possible that IE may take advantage of these things in the future, hopefully, and you won't learn what CSS truly has to offer in the dummies books.
I would definitely recommend looking at WROX CSS books such as "Professional CSS..." and "Accessible XHTML and CSS Web Sites Problem Design Solution" after reading this book. Other good books would be Jeremy Keith's "DOM Scripting...", which is geared towards CSS guys, and Dan Cederhom's "Bulletproof Web Design..."
That being said, the Dummies book, in my opinion is the easiest starting point... just be prepared to do more reading.... lots more.