I would say it's very conversational in narration, akin to the author's previous title (I suppose you are reading at the moment), so it is easy to grasp the ideas, although I just concentrate on this book a few days ago.
It's kinda quick primer on web ui design, I would say ideal for busy developers/programmers in aspects like usability, IA, accessibility, UX. A good refresher too for people who already knows these stuffs.
If you are looking for something more profound I suggest the following:
Designing Web Navigation: Optimizing the User Experience
(http://www.bookjetty.com/books/0596528108)
Designing Interfaces
(http://www.bookjetty.com/books/0596008031)
The Practical Guide to Information Design
(http://www.bookjetty.com/books/047166295X)
Universal Principles of Design: 100 Ways to Enhance Usability, Influence Perception, Increase Appeal, Make Better Design Decisions, and Teach Through Design
(http://www.bookjetty.com/books/1592530079)