The book was published in 2004 and it shows - many things are phrased as open questions, but it does give some overview about the topics of the 'layer cake', i.e. RDF, Ontologies, Logic/Inference, Trust, in addition speaking about Semantic Web Services & Agents.
Kind of an introduction to the topic, but a bit dated and superficial.
The author also very much likes Topic Maps and always presents them as interesting alternatives, whereas I get the feeling that - at least now - RDF is the standard to go with.