Barnes & Noble Rewards Program
B&N has a rewards program, but it is not free. It costs just under $50 to join for the year and that entitles you to 10% off on just about everything, 20% off hardcovers, and up to 40% off on bestselling hardcovers.
Right now they are running a special where you'll get $50 in B&N coupons when you join, which offsets the membership cost.
Barnes & Noble Return and Price Match Policies
B&N items bought online can be returned in stores if you bring the packaging with you. They have a pretty standards 14-day return policy which you can read about here.