You should check out the Iain M. Banks novel, Against a Dark Background. It's set outside of his Culture Universe, in a planetary system orbiting an intergalact

You should check out the Iain M. Banks novel, Against a Dark Background. It's set outside of his Culture Universe, in a planetary system orbiting an intergalactic star. There is no FTL so humanity is effectively trapped. I wish that Banks had expanded on the idea with further novels as I really enjoyed reading about the cyclical rise and fall of societies while humanity explored different social/political structures, hoping to achieve some form of long-term stability.