Even 8 years after Gravity Falls ended, I still have questions about the show's many mysteries and characters, which is what makes The Book of Bill so exciting. Penned by series creator Alex Hirsch, the tie-in text is written from Bill Cipher's point of view. Although many of us didn't initially realize what Gravity Falls' end-credits cryptograms were teasing, Bill, a triangle-shaped interdimensional demon, was the show's overarching antagonist. The top hat-wearing, one-eyed menace is capable of infiltrating and taking over peoples' minds, which makes him a massive threat even by Gravity Falls standards.

The series finale, "Weirdmageddon 3: Take Back the Falls," Gravity Falls' core characters twins Dipper and Mabel Pines, their Great Uncle "Grunkle" Stan, and Stan's estranged brother, Ford try to thwart Bill Cipher's evil plans. The profoundly unhinged and wildly irreverent Bill Cipher is one of my favorite TV show villains. Although his goals are deceptively simple,...