My Kelby book arrived today. It's one of several PSE books I've got and imo one of the better, more useful ones, though the first v3 I've seen.
Kelby states that his book is oriented toward Windows, but Mac users should simply skip Chapter Two on the Organizer.
The reality is that the Mac and PC versions are otherwise more similar than different. Other than some obvious keystroke differences I've seen nothing in the book that would confuse a new PSE3 user.
To me it does not seem like a strict beginner's book, but more an intermediate level read. That's a good thing, as intelligent Mac users such as you don't need to be told the simple stuff--he gets to how it can work on your photos.
There are good learning sources other than books if you are so inclined. You'll find many tutorials on the web and be sure to look at Adobe's PSE users' forum. It is well moderated, friendly, and informative. Their web site is much more satisfactory than the available Usenet presentation of it, plus all the useless Usenet trash that happens.
Have fun with PSE3. It's a great program and real bargain in software. Set yourself a project to accomplish on some of your photos and learn how to make it happen!