Summary: Almost-human, about modern tech, oppressive social hierarchy and empire, has slavery.

Longerform, some features of this setting:

Population is very-similar-to-humans.

One difference from humans is strata. Everyone has a stratum, which is a value-for-a-variable type feature of them. There are four of them, referred to as Alpha, Beta, Iota, and Omega. They are not directly detectable to normal senses. The scientific explanation is something-something-brainwaves. Some people can just detect them by being around a person. In early history this was very common; by the modern day it is very rare. Technology exists that can read strata but only until about age five. Strata are generally hereditary but not perfectly so.

There is a de-jur and de-facto hierarchy based on strata, various stereotypes of them, etc. Strata tend to go with some features of body language and other nonverbals. Some people will notice this explicitly, but most are aware of it subconsciously.

Another difference from humans is the presence of Protectors, who are psychologically inherent strong altruists. Protectors read in the same 'field' as strata, but are a different thing - they come in all strata.

Society

There is a large oppressive empire.

Slavery is legal and present. Iotas and Omegas can be enslaved either as punishment for a crime, or if their family sells them into slavery. The children of slave Iotas and Omegas are slaves. Betas can only be enslaved as punishment for a crime. The children of slave Betas are free, and are usually taken away by the government and raised in orphanages. Alphas who commit crimes where the sentence would be enslavement are not sold. They are kept as slaves by government organizations, and tortured to the complete breaking point first.

'Commercial' slavery is a sentence for political crimes. Violent etc. criminals are enslaved to the state, and sent to hard labor.

Everyone except slaves wears citizen's cards, which are basically nametags.