Me vs. the multiverse

"It all starts with a note folded into the shape of an origami octopus: Hi, Me. Yes, you. You're me, and I'm you. If you believe this and the other origami notes that follow--which middle schooler Meade Macon absolutely, positively does NOT--the concept of parallel dimensions is true, and there is a convention full of alternate versions of Meade waiting for his RSVP. It's got to be a joke. Except . . . the octopus is an origami fold Meade thought...