From now until June 17th, Barnes & Noble is offering a Father's Day promotion that will save US customers $20 when purchasing either a Nook Simple Touch or Nook Color with a MasterCard. The deal is available both online and at B&N's retail locations. With the discount, the bookseller's e-ink reader can be had for $79 — putting it on equal footing with Amazon's cheapest Kindle — while the Nook Color drops to $149. In-store buyers will receive the discount via a printable coupon and web shoppers can expect an instant coupon code at checkout. Unfortunately neither the new Nook Simple Touch with Glowlight or Nook Tablet are part of the promotion. Still, if dad's looking to transition into the world of ebooks, this sounds like a good time to make the leap. That's assuming you won't be taking advantage of the savings yourself.