I feel like a setting primer should have more hooks. What is valuable in this world? What are the pcs likely to be after? Honor? Glory? Gold? Political power? Are there things a dragonborn would never value, that adventurers usually would? Or vice versa?
What about law and order? Are certain people untouchable, or outcats in society? What about the consequences of the law? Are there white collar slavers who operate scams to entrap indentured servants? How powerful are the churches?
What are the threats and changes that the empire is facing? Is it stagnating? Evolving? Is democracy on the wane, or on the rise? Are the govenors feuding, or uniting in a power block that opposes the senate? Are the empire's borders expanding or contracting?
Who are these indentured servants? Are they dragonborn? Why not humans, or dwarves? If not slaves, how are humans treated? Killed on sight? Are the dragonborn genocidal, or do they seek to spread their culture through new cities and settlements?
Where are the points of conflict or adventure in the setting? Is it as simple as the wilderness between the cities, in which case, what's there? The same old Ruins? Tribal lands? Ancient barrows and menhirs? Are there alternative adventure locales, like the ancient mausoleums, sewers, and old streets beneath the surface of the cities?