The story/novel I've been writing hasn't needed a serious description of how the society it's (mostly) written about works - until now. I thought I'd post a few thoughts, and maybe some people would have some other ideas.
It's loosely based on the Victorian period of the Great British 'empire', but without the hangups about sex. For some reason, the male/female birthrate is skewed towards females, with the ratio about 3:1 or so, and very low generally. The society is divided into 3 classes: lower (unskilled workers), middle (bureaucracy, military, merchant) and nobility (mostly useless). The gender imbalance leads to some unusual customs, particularly since there is a very strong bias towards male leadership, and against women working (at least without extensive male supervision). Two or three wives are customary, for example. Many of the surplus lower class females have to sell themselves into indentured servitude.
The Empire has two main neighbors, one is religious fanatics who hate them, the other is insectoid aliens who are indifferent.
Technological progress is mostly stalled, and has been for about 400 - 500 years.
About 500 years ago, the Empire was pushed out of 2/3rd's of its territory, and most of the tech on all the planets was destroyed. The abandoned areas and the diminished Empire took about 400 years to rediscover the lost technology, but went in very different directions.