This thesis explores how library practice has been impacted by linked (open) data. For libraries, adopting linked data principles means moving away from the long-established reality of MARC-formats and opening up their information resources to the internet. While the transformation of library systems to linked data is often described as the necessary next step for the library community promising enormous benefits, the reality of the transformation process is a challenging one. This thesis employs an interview study at the National Library of Sweden, the first national library worldwide that has adopted linked data as its core data-model, to provide deeper insights into how linked data is affecting the current work practices of library professionals from their own perspectives. The findings suggest that linked data is significantly impacting library practice in a multitude of ways, fundamentally changing knowledge and information organization in the digital age. While linked data is still in the beginning stages of its implementation in the library community as a whole, the interviewed library professionals are confident about the benefits the transformation will bring eventually. While there are still many challenges and obstacles to tackle there is a strong believe that the advertised promises of linked data will come true in time. Furthermore, the results of the study suggest that linked data is only part of a paradigm-shifting change currently happening in the knowledge and information organization community, accompanied by many other developments that are as a whole fundamentally changing how information is organized, managed, shared and even perceived in today’s digital information environment of the internet.