The purpose of the thesis is to shed light on how the management of municipal museums views their museum libraries, including the libraries' function within the operations, their contribution to, and impact on the museum's identity. Seven managers at municipal museums in five different locations in Sweden were interviewed. The material was processed through qualitative interview analysis, and a theoretic framework of legitimacy and documentality resulting in four categories with twelve subcategories. The study shows that the management considers the museum libraries to be primarily important for the internal operations of the museum, sometimes more so than initially apparent. When the libraries have been open to researchers and the public, they have also had a significant impact on the museum's external image and reputation. The management indicated that investments in the libraries have significantly improved the museum's professional reputation. A recurring theme in the study is the lack of consensus on when a book should be regarded as an artifact in the library or as an object to be registered in the museum's collections.