I'm a bit disappointed that in the end there was no twist or surprising revelation. Just a 'big ghost ate small ghosts, big ghost got strong, big ghost used curse' explanation. Naomi even mentioned her late grandmother living nearby, but it never came up again afterwards, which I thought was going to be a clever use of Chekhov's gun.
Oh well, it was still fun to read. I'm curious about the next arc that is awaiting these kids.