Request #567 From re

Read this children’s/YA book in a random used bookstore growing up in Lawrence, KS, have been trying to find it again for the last ~15 years. Maybe the cover was red? The main theme is solipsism, which is referenced by name numerous times (how I learned the word solipsism as a kid, lol) — the main character is a teen, can’t remember if girl or boy, who becomes convinced that their whole reality is a fiction invented by their brain, and people/scenes will just stop existing once they leave them. They try various things to test this hypothesis, like leaving a room and then quickly going back in, to see if they can catch things disappearing. Their parents make a living traveling around selling things at craft fairs. They move somewhere, I think California, and rent a house from a family that had two children, a girl and a boy — the girl’s bedroom is stereotypically pink and frilly, the boy’s bedroom has model airplanes hanging from the ceiling, there’s a big American flag in the living room. One particular scene I remember, the kid goes down to a river and sees a fisherman in a boat and a kingfisher, tries for awhile to determine whether the fisherman and kingfisher will continue to exist when they leave/look away … My memory of actual plot points is fuzzy but I think towards the end they are attending a craft fair