Has a tendency to throw up figures containing terminology or concepts that haven't been defined yet, which can be confusing.
Also uses some terms in contradiction to the definitions they provide. For example, they first define "foaf" to mean "Friend of a Friend," but then go on to use "foaf" for all kinds of relations that are not between friends, e.g. "isi:mayank_kijriwal" --foaf:name-->"Mayank Kejriwal". (And it throws up a URL for "foaf" when no such URLs have been mentioned.)
In some respects, this book could be a good refresher who those who are already familiar with the material by other means, but a reader new to the topic, this inconsistency of terminology and the tendency to things to with no prior explanation makes for a choppy experience.
Another serious issue is that the book is exclusively focussed on web-based knowledge. So after slogging through Chapter 2 about RDF, one finds that the chapter on "Domain Discovery" concerns *only* trawling the web. There is absolutely nothing about conducting interviews of organizations or individuals to obtain and represent their knowledge.