A content specification containing a data structure describing a digital volume to be incorporated into a digital library is received. A digital volume is a digital representation of human-readable content, such as a digitized book. Volume content of the digital volume is obtained based on references in the content specification to the locations of the volume content. The volume content is indexed based at least in part on information in the content specification, including volume metadata such as the title or author of the volume. The content specification includes markup language elements, each element specifying information about the digital volume. A plurality of tags are associated with the markup language elements. A structural tag specifies structural information associated with the digital volume, including the location of a portion of volume content of the digital volume. A metadata tag specifies metadata describing or identifying the digital volume.