Someone from Earth is about to be sent off to the cosmere. They've read your first Stormlight book, but they've never really taken time to really dig deep and find out about how it sits in the overall "cosmere", so they're totally unprepared. What basic concepts regarding shards, magic systems and world hopping do you think are most important?
The first, most important thing to say to the person who's being sent there is to enjoy the story you're in. All of the cosmere stuff, the interconnection between my books and all these wonderful little things, are right now mostly Easter eggs. Which means that if you spend the whole book only worried about that, you're going to miss the beauty and fun that is the book that you're part of. I often say to people, don't worry if you read them "out of order," because it's all Easter eggs right now. Don't worry and stress if you miss something about the cosmere, because while someday that might be important, you first need to enjoy the book that you're part of. But the primer I'd give to this person is that the worlds are connected. If you show up on a planet and there's a guy named Hoid around, then be very afraid, because you're someplace very dangerous.