Not quite science fiction, the story is offbeat and psychological. Antsy, Howe, Ira, and the Schwa himself investigate the Schwa Effect (his seeming invisibility). Four out of five people don’t notice him standing right next to them. Not even when he stands in the bathroom with an orange sombrero and a cat costume and sings loudly.
The friends start with experimentation of the Schwa Effect, and then investigate the disappearance of the Schwa’s mother by interviewing observers.
Quite an unusual book. It’s been added to my YA Horizons list.