The Mercer Island Library is a full-service public library and part of the King County Library System (KCLS). The library was remodeled in the 1990s, and is an important center of learning and culture in the community. In 2009, it circulated more than 400,000 items and counted more than 200,000 visitors.
The library is supported by the active Friends of the Mercer Island Library. Its successful book sales events fund 75% of the programs offered here each year, including popular programming for children and teens.