Quite a bit more. The whole thing is essentially what I would probably call a sociological horror, a horror story in which society is the monster. It is a break-down on the very idea of harem themes. The premise is that this is a world in which there is 1 man for every 999 women, men make up 0.1% of the population. It then takes that premise and extrapolates out, quite credibly, how society would form itself around that as the basis. Let's just say the results are not very pleasant. It is a concept that you would hear about as a man and think that would be a wonderland that would favor you in every way, but the reality of the situation is absolutely terrifying and leaves you vicariously regretting the fact you ever thought that would be a nice idea through the psychological anguish that the protagonist and the members of his harem are put through.
If you go into it just wanting smut and material to get off to, my recommendation is that you should actually stay away from this series. It is one of those reads that are very unpleasant in a good way. You will not get your jollies off of it, but if you are the type who likes something mentally stimulating but also horrifying like Psycho Pass or something along those lines, then you will absolutely love this series. (Also, Ok, MAYBE you can get a few jollies off of this series. It is a smut series with a smut premise despite the fact that it gets taken down a very dark road. It DOES have full-blown H scenes that give full erotic detail, and they are (mostly) not rape scenes. They are very consensual and positive.)
EDIT: I do mean this series REALLY goes deep on it's commitment to society building around this premise. It goes into things like class warfare with ways that the rich monopolize the men giving the lower class women little chance to reproduce and leading them to desperate measures. The rich do things like granting free education to all the men at the best schools available. Sounds good and all, but what they are really trying to do is get the men used to the standards of the upper class and raise their expectations so they are less likely to choose to impregnate any lower class women. There are also feminists in this world who do not like the idea of men having the freedom to choose who they impregnate since they think it gives men too much power that they exploit and hold over women, and they are constantly trying to enact laws to deny men any choice on who they copulate with. It gets pretty crazy.