The Watertown Free Public Library is holding its first 5-kilometer fund-raising road race Saturday at 9 a.m. The Book It and Run 5K will begin near Saltonstall Park next to the library, and will loop along Main Street, Chapman Street, Orchard Street and Church Street. Registration costs $20 for adults, and $15 for ages 18 or younger. The first 300 registered participants will receive a T-shirt. For more information, visit www.watertownlib.org.