The triannual Mercer County District Library book sale will be open today from 9 a.m. to 8 p.m. and will also be held on Saturday from 9 a.m. to 5 p.m. in the book barn next to the library. On Saturday, customers can purchase a blue library bag for $3 and fill it with as many books, CDs and DVDs as they can fit. Proceeds from the book sale support the library's children's, teen, and adult summer reading programs, as well as other library-sponsored programs.