The lost generation ship is a concept in SF that appeals to me as a GM because of the ability to mix setting types on different decks of the ship and to create what are in effect dungeon crawls in exploring the various areas.
I've been inspired in this by the original Metamorphosis Alpha game, which was one of the first RPG I bought back in the 1970s. The literary inspirations comes from Brian Aldiss' Non-stop, published in the US originally as Starship. There are not a huge amount of stories set in this specific setting apart from Non-stop and Robert Heinlein's Orphans of the Sky, but I have found Aldiss' stories in the Hellonica series of novels and Hothouse as useful inspirations.
In my choice of title I have used the idea of the characters not being aware of where they are and the ceiling above the deck where the characters above is the seen as the sky. This means that often there will be a low ceiling making flying mutations less useful than in a conventionally Earth setting, this means that I've opted to ban the Complete Wing Development and Psionic Flight mutations.
I'll discuss this some more in another part where I'll set out my base assumptions about the setting and start to develop some of the details of the settings.