(And the secrecy exists in the drama too, but a) IMO it's less fundamental because the whole Netherworld and ghosts aspect is closer to home than Dixing - it's the ghosts of dead humans, after all, and b) by the end of the drama it's all been blown wide open and public. I don't think that happens in the novel - or does it?)

Yeah, it's all completely different. I mean, a lot of people believe in ghosts as part of the natural order, and pray to their ancestors, so that isn't really a secret in the same way. And the ghosts of dead humans aren't supposed to stay in the mortal world, and can't live good lives there, so that's different, too. It's the yao that seem to be the most hidden part, to me; do ordinary people know about them?