As a professional Information Architect (IA), I try to read as many design books as I can, and this is one I will recommend again and again, mainly for it's refreshing lack of pretense and it's easy-to-follow style.
For the Non-IA, read this book because it "demystifies" IA on many levels. It explains what an Information Architect does, why you might need one, and does a great job of discussing all of the possible deliverables an IA might produce and why. If you're overwhelmed with design "buzzword bingo", this book explains a lot, and in easy-to-understand terms.
For the IA, read this book for the up-to-the-minute tools and techniques. She doesn't dictate a fixed methodology or hard-and-fast rules, instead, she presents a toolbox and guidelines for using them. I found the chapters on Personas and Taxonomies/Controlled Vocabularies especially helpful. She demonstrates that she's been out there working in the real word when she offers advice on overcoming creative blocks, working with people, and how to get your ideas across to (not always supportive) groups of people.
Many IAs will see themselves in this book ("I've created wireframes that look just like that" or "Yes, I've found that too!"), but the real value here might be recommending this book to your favorite Project Manager or Developer so they can gain a little more insight into what you do and go to bat for you on the next collaborative project.