Amazon just ran a Groupon last week, and it looks like Barnes and Noble is following suit today with the following deal:
That's right! Spend $10 on a Barnes and Noble Groupon and receive $20 in store credit. Basically, what you're paying for here is a 50% off coupon, which is usually a pretty good deal for bibliophiles. Make sure to read the fine print, as it looks like this expires April 10th, or at least the value is reduced to $10, making the discount disappear.
Knowing me, this will be spent sometime this weekend. The limit is 1 per customer, and it doesn't look like it will let you buy one as a gift, so just make sure to pass the deal along to your friends and family.