You must join their free loyalty program, called Borders Rewards, to use the coupon. Last time I checked, you can only join in stores for some reason.
Print the Borders coupon or online use code BSL7108N. One per person. The coupon is also valid at Borders.com, Borders Express, and Waldenbooks.
Caveats: coupon cannot be combined with any other offer, excludes previous purchases, special orders, gift cards, newspapers, magazines, comics, coupon books, eBooks, digital downloads, video games, vinyl LPs, self-publishing programs, Smartbox products, Rosetta Stone software, and all electronics,