So I see in many of Rick's books that often a shop will offer a discount of some sort for purchases. It mentions that you need to show your RS guidebook.
My question is, do you need to have the actual paperback in hands for this? I have a couple of his guidebooks in digital form to make it easier while we are abroad. Would it suffice to show the discount stated on my phone (Kindle app) or do I need to buy the paperbacks?