Based on the positive reviews, I bought the book and read it. The book is an amazing waste of paper. The contents of the book can be summarized as advocating a certain way of coding Web sites, with one partially worked example. The book could have been a 5 page white paper.
The book advocates writing Web sites using XHTML, and using CSS for layout information (styles.) There is some discussion of being careful to write structural tags instead of specific markup. As an example of what this means, if you want to display a list without bullets or numbering, you should tag the list items using li.../li, and write an appropriate CSS style for the list that produces the look you want. This is better than writing individual items separated using br to force formatting. By the way, Zeldman gives this specific example, without bothering to show how to write the appropriate CSS styles.
While the book contains many recommendations, it provides few worked examples, and essentially no reference information. When you read the book, you learn that you should create Web pages in a certain manner, but not how to do it. Chapter 6 contains an actual example of what Zeldman thinks you should write. It begins on page 153 of the book. The preceding 1/3 of the book contains lots of opinions, but little information. Chapter 6 contains useful information, as does chapter 8 (the first part of an example, showing the XHTML of the single worked example in the book), and chapter 10 (which contains the corresponding CSS to chapter 8's XHTML). Most of the remaining chapters have some information.
What I generally expect in a book that explains a topic is a description, a worked example, some references for more extensive information, and discussions of good and bad alternatives.
Zeldman's book instead provides many chapters of opinionated ramblings about his view of the current state of the Web design world, how the world got that way, and what is wrong with it. These ramblings are written assuming that the reader cares or has a reason to care about how the Web design world got to the state that Zeldman thinks it is in, and that the reader fundamentally understands the topic, which Zeldman discusses in obscure references. These ramblings are then followed by one or two partial examples, no reference information, then more ramblings about the topic, now that you have been presented with Zeldman's solution.
If you want to learn how to design with CSS, there are many alternative books, and of course there are the W3C standards themselves. What is good about Zeldman's book is that he addresses the issue of how to design pages using CSS/XHTML, rather than simply how to code the CSS. The problem with the book is that he provides almost no information about how to do this.