SPOILERS for Gravity Falls' season 2 & finale + MLP:FiM season 6: "The Crystalling". One year after Weirdmageddon, the Pines reunite in Gravity Falls for another summer of adventure. A fall into Equestria as ponies wasn't what they had in mind.
They thought it was just another exciting story when the new book came out. But Twilight Sparkle and her friends soon learn that all fiction hides truths. Some more deadly then others.