While I don't own 'Gravity Falls: Dipper and Mabel's Guide to Mystery', I borrowed it from a friend and was struck by how much it feels like a direct artifact from the show. The book mainly serves as an in-universe manual where Dipper and Mabel documented their adventures. Its big secrets aren't huge revelations about Bill Cipher, but rather a delightful layer of world-building. You see their direct reactions to monsters and locations, which can be surprisingly poignant, like Dipper’s increasingly frantic notes about Gideon or Mabel’s glittery commentary on the Multibear.
What I really dug were the smaller, almost throwaway details. There’s a page where they try to classify the different types of gnomes, and in the margin, there’s a tiny, frantic scribble from Soos about 'not the teeth!' that had me laughing. It doesn’t contain a hidden code breaking the whole series, but it reinforces the show’s heart—the weirdness filtered through two kids’ very different perspectives. Finding it felt less like unlocking a vault and more like discovering their summer scrapbook, coffee stains and all.