We describe the intellectual and physical properties of books as manifestations, expressions and works and assess the current indexing and metadata structure of monographs in the Book Citation Index (BKCI). Our focus is on the interrelationship of these properties in light of the Functional Requirements for Bibliographic Records (FRBR). Data pertaining to monographs were collected from the Danish PURE repository system as well as the BKCI (2005-2015) via their International Standard Book Numbers (ISBNs). Each ISBN was then matched to the same ISBN and family-related ISBNs cataloged in two additional databases: OCLC-WorldCat and Goodreads. With the retrieval of all family-related ISBNs, we were able to determine the number of monograph expressions present in the BKCI and their collective relationship to one work. Our results show that the majority of missing expressions from the BKCI are emblematic (i.e., first editions of monographs) and that both the indexing and metadata structure of this commercial database could significantly improve with the introduction of distinct expression IDs (i.e., for every distinct editions) and unifying work-related IDs. This improved metadata structure would support the collection of more accurate publication and citation counts for monographs and has implications for developing new indicators based on bibliographic levels.