The Epilogue is a standout chapter in It because, although there's some weird supernatural stuff going down…it doesn't kill or maim or terrify anyone.
At the end of It, Bill's wife Audra is catatonic. She's looked into It-Spider's eyes and been caught in the deadlights, the trippy alternate dimension that It controls. Bill has hauled her out of the plane, nursed her back at Mike's place, had her watch all sorts of fun '80s daytime TV…and she still hasn't snapped back to life.
Things aren't helped by the fact that Bill's memory of everything—the Losers, It, the sewers—is fading fast. So is Mike's. They realize they only have a few days before they forget everything…which would include an understanding of why Audra is catatonic.
Bill has a last-minute inspiration. He gets out his old bike, Silver, and sits Audra down on the carrier behind the seat. He mounts the bike, and her hands creep around his waist. That's Audra's first independent movement in a week! He proceeds to make like his eleven-year-old self and ride recklessly and incredibly quickly. He's infused with a feeling of his youth…and it magically wakes Audra up. They dismount the bike and make out.
In the very last paragraph of the book, Bill wakes up from a dream about his childhood. When this happens, he thinks that he'll write it down some day. But ultimately, he always forgets.
So what's up with this? It's a bittersweet couple of scenes that show the dual side of the memory of youth and childhood. Memories of childhood can wake you up—like Audra snapping out of her reverie—but, ultimately, childhood memories are a dream you can never truly grasp.