Managing and distributing published information is traditionally the mission of libraries. But in times of digital information provisioning and personalized content delivery, the processes to fulfill this mission have to be re-considered. Beyond simple keyword indexing using library categorization systems, digital corpora need to be preprocessed for later access directly by the end user. Thus, major functions of the classical librarian like assessing the actual information need and mediating between the library categorization and the end user, are to some degree bypassed and have to be compensated for. Moreover, also the quality control of a digital library’s metadata annotations used for subsequent querying of collections has to be guaranteed. In this paper we discuss the importance of metadata quality control for large eBook collections.