The emphasis in the title is definitely on the first word - programming. This is a book for web developers, not web designers. For programmers looking to the future of the web and how to sematically connect all of the disparate data that such a huge data resource contains then this book makes an extremely useful introduction to a technology that may well be the future direction of the web.
According to this book Web 3.0 is the semantic web and it will be coming soon to a web browser near you. The book starts out describing what semantics is and how the web needs to be able to handle an expanding collection of semantic data that cannot fit a conventional relational database design. To cater fully for what the semantic web needs to become the relationships themselves become data that needs to be stored.
After introducing the concepts the book moves on to a discussion of technologies that have already been developed that make the semantic web possible. The technologies mentioned include RDF, N-Triples, RDF/XML, RDFa, SPARQL, Freebase, OWL, Protege, microformats, and Sesame. Some of these are programming languages, some database query languages, and some markup languages. Some of the markup works with existing HTML 4.01 web pages (although it will fail validation) as well as XHTML 1.0 (where the extensible nature of the language allows for such interactions between different markup languages).
The information that the book presents clearly demonstrates that a web page is not a stand alone element any more and that extensibility to work with other markup languages is the way of the future. The examples that the book gives makes it clear that this combination of technology is a very real future and not just something that a few people hope might happen.
The book concludes by showing how the semantic web is built up of a lot of different layers not all of which currently exist but goes on to explain how by using those layers that do already exist we are moving ever closer to what this web 3.0 technology promises.