This book gives an indepth look at this new field along with loads of information on how to design successful web sites.
The biggest problem with this book is that anyone who hasn't heard of Information Architecture before is unlikely to even look at this book. Anyone who has any part in designing a web site of more than a couple of pages will be really missing out on a huge amount of useful info though if they don't read this book.
The second biggest problem that the book has is the first chapter or so. When you start reading the book it starts out talking in rather general terms and you might find yourself thinking "so what" and be tempted to stop reading. As you get further into the book though the information becomes far more specific and far more interesting to read. There are a huge number of interesting ideas and concepts related to web design that are discussed in great detail in this book and for those fortunate enough to make it into the main portion of the book there is plenty to learn.
Whether you are actually responsible for those parts of the design that come under the label of "Information Architecture" or whether your particular job is in some other area of web site design and implementation, the information presented in this book will provide you with enormous help in getting your job done better. At the very least you will have a better idea of where your contribution fits into the overall picture.