PREFIX dc: <http://purl.org/dc/terms/>
PREFIX pgt: <http://www.gutenberg.org/2009/pgterms/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
SELECT ?title ?subject ?author WHERE {
    ?book rdf:type pgt:ebook .
    ?book dc:title ?title .
    ?book dc:subject ?sub . ?sub rdf:value ?subject .
    ?book dc:creator ?cre . ?cre pgt:name ?author .
}