I agree with another reviewer who said that he found the material rather dated. It is.
However, I found some of that dated material fascinating -- the author's discussion of hypertext systems before the Web ever existed, the author's predictions/descriptions of handheld computers before the Palm organizers ever existed, etc.
Also, many of the "boring everyday examples" that another reviewer hated (such as doors, legos, stoves, faucets, and so on) were exactly what I needed. For example, a discussion of an ice cream menu helped me immensely with a corporate Web site I maintain. That's because the author went into detail about "decision trees" and how people handle lists of information.
In chapter 5, the discussion about the differences between "slips" and "mistakes" (which I thought were the same) will help me build better user interfaces, because I now know why people have problems with some interfaces, and how to resolve those problems.
I had also never heard of "forcing functions." I've used forcing functions, but I didn't know I was using them, and I didn't have the concepts clear enough to make them effective.
In summary, the book is dated but good. Couple this book with a book like "Information Architecture For The World Wide Web" or "Web Site Usability" and an average Web designer could become an excellent Web designer.