5 needed to calculate an average
(Rec applies to the earlier volumes of both, later volumes are vastly different)
Marginal and Andromeda Stories are early-80s science fiction manga from extremely influential shoujo mangaka. Both are soft sci-fi, and tend to blur the distinction between science fiction and fantasy. Both are set in a desert dystopia loosely modeled after a mish-mash of Middle Eastern cultures.
I liked Marginal much better- the story and characters seemed better developed/less generic, while Andromeda Stories was kind of hokey (it hasn't aged as well).
In the Tokugawa era, the dreaded redface pox is devastating the country's population of young men, and after a few generations, the gender ratio has fallen to roughly one male for every four females. Since sons rarely survive to adulthood, family trades are now passed from mother to daughter, and women hold even important governmental positions. In order to prevent the rest of the world from discovering this state of affairs, Japan institutes a strict isolationist policy, and female officials adopt masculine names so that even the official records don't reveal what's happening. Though the outside word is suffering from a shortage of marriageable men, the inner chambers of Edo castle are a lavish place, filled with hundreds of men who serve both as an emergency standing army, and also as the personal harem for the new shogun - a woman named Yoshimune who is determined to fix the rampant inequality and wastefulness of her country.
Another excellent political shoujo manga about societies with extremely uneven gender ratios. Ooku's society is largely female (except for the predominantly male inner chambers), while Marginal's has one Mother and everyone else is male (like a modified ant/bee structure).
Ooku is historical, and Marginal is a sort of post-apocalyptic sci-fi, but if you liked the political drama, gendered themes, and extremely fleshed out setting/culture of one, check out the other.