With the second edition, Morville and Rosenfeld have met a pretty significant challenge: surpassing their first book. The new edition is chock full of great new chapters on topics both technical and creative.
By covering subjects like thesauri, CVs, and metadata, while at the same time tackling headfirst "big picture" ideas of information architecture, the two authors are to be commended for writing a book that is at once instructive to advanced practioners yet still recommendable to strategists, designers, programmers, and others who might have only a vague notion of information architecture. And the chapter on business strategy is as good an introduction as I've read in any business book.
This book is the closest anyone has come to a single book addressing all of the complexity and challenges of organizing, structuring, and managing large scale Web sites, and does so with clear, easy-to-read prose eshewing jargon and consultant-speak. Quite an accomplishment, indeed!