It seems to be a perfectly bogstand piece of fantasy fiction. Princes and their squires in a feudal everyworld. Sure there are odd hints about “the wall” but the hints that things may not be what they seem are laid on delicately until the reader is shocked to find that this fantasy world is actually taking place in the far future on a giant spaceship.
Except they aren’t surprised at all because the book is called Mothership, the cover has a spaceship on it, and a blurb on the back that gives away every aspect of this twist.
I was talking aspects of plot development with some friends the other day, wondering that the fact that something I am writing takes a long time to get to anything that could be called plot. It was agreed that as long as the writing and characters are good it doesn’t matter, they will already know the plot from the blurb. Just make sure you use the blurb as a force for good, don’t let it undermine your hard work.