There are two great book sales on Memorial Day, so — before or after you spend some time paying tribute to loved ones — check these out:
1. Boylston Public Library book sale (across from the Common, where there is usually a lot of entertainment for kids) from 9am-2pm; the prices are usually decent and the selection is quite good.
2. Not too far away from the Boylston Library book sale is the First Parish Unitarian Universalist in Northborough Memorial Day Fair, which usually has a great book (and plant) sale from 10am-3pm. Great prices and selection.