Covering the theory, technical components and applications of the Semantic Web, this book’s unrivalled coverage includes the latest on W3C standards such as OWL 2, and discusses new projects such as DBpedia. It also shows how to put theory into practice.
A Developer's Guide to the Semantic Web is a fairly intensive overview of the various components of semweb technology. This exhaustiveness comes at the cost of clarity, however. This is a useful reference for working with OWL and RDF, somewhat less useful for SPARQL, but good as an indepth overview of frequently used ontologies: FOAF, SKOS, Dublin Core and others. I'd recommend this for the bookshelf of a working ontologist, but would hold it off for a bit if you are entering the field.