Longwood Public Library readers must soon go the extra mile to sift through books.

The Middle Island library will start to relocate this week to a temporary site at the King Kullen shopping center -- one mile east of its current location -- for 18 months as it undergoes a nearly $18 million renovation, officials said.

Voters approved the $17,986,000 bond to fund the expansion last October by a 698 to 394 margin. The library, at 800 Middle Country Rd., will be closed this week.

The project includes a 15,000 square-foot expansion, extra outdoor space and new energy efficient components such as natural day lighting, officials said.

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"Our primary mission is to serve readers . . . children and parents," said library director Suzanne Johnson.

Officials say the building was constructed in the late 1980s, but Longwood's population has increased, outgrowing the library.

In 2011, more than 350,000 people visited the library and borrowed nearly 800,000 items, while more than 50,000 people utilized programs there.

Johnson said materials are often stacked too high on shelves and a lack of space has restricted programs.