I found this bookmark for that store tucked away inside a 1974 edition of Pat Boone's "A Miracle a Day Keeps the Devil Away."
The store was located at 1323 Greenville Avenue, within the Staunton Plaza Shopping Center.
According to Google, businesses now in that general area include Country Cooking Restaurant, Dockers, Head Over Heels, Montie's Collectibles, Red Lobster and the Virginia Liquor Store.
But there's nothing at all on Google about Sath Book Shop.
1. These two previous posts also mention Staunton: