Idk if this is something really obvious that everyone else knew immediately, but here is my latest realisation abt the Locked Tomb series.

(I have not read Nona yet)

Is it set in a future version of our solar system?

On my first read of GtN and HtN, I wasn’t really thinking about it. It definitely seemed possible, with all the historic culture that Gideon and Harrow discover in Canaan House and the Mithraeum. Towards the end of HtN it seems pretty likely, with characters named after eminem lyrics.

However I am now rereading GtN and I think I have some pretty conclusive evidence.

Nine houses, nine planets in our solar system, IF you include Pluto. This correlates very nicely with the Ninth House, with how it wasn’t supposed to exist and is regarded differently to the other eight houses. I propose that the Ninth House is on Pluto, dark, cold, small, the last to be inhabited, it’s status as part of the solar system constantly debated.

This of course could be a coincidence, there’s a lot of star systems with nine planets. However the position of the first house seems much too specific to be a coincidence.

I initially assumed that the planets were numbered according to their distance from the sun, however this is evidently not the case. It seems likely that they are instead named according to the order in which they were inhabited. The First House is the ruling house because it is the base planet, where everyone originally came from. When Gideon and Harrow arrive at Canaan House, we find out that there are two houses closer to the sun, so the First is therefore the third planet from the sun, which would make it Earth.

On my first reading, I didn’t recognise it as Earth because it’s covered in water. However this is a post-climate-change version of the Earth, with higher seas and drastically reduced land mass. (There’s probably some land somewhere though)

Combine that with how familiar all the pre-resurrection artefacts seem, and it’s being pretty strongly implied that GtN is set right here.