Anything that requires me to have to use my phone while I practice my craft is a negative to me. I don't mind getting information digitally, but the minute I pick up my phone I'm immediately at risk of getting distracted by a million other apps/notifications/messages. So, I think it would be great to offer both options to people. Charge a bit more for a deck with the physical book or give someone a link/qr code to the online version to download and allow them to purchase just the deck.