I'm trying to identify a book I read somewhere in the 90s. It was a far future story with spaceships, interstellar travel, a rebellion and similar generic sci-fi elements.
What made it somewhat unique was the use of partial or full sex changes during the course of events. People were sex-changed as a punishment or to control them. One guy's male genitalia were replaced with female parts to – if I remember correctly – punish him for some failure. Another guy, a kind of leader for some kind of rebel group, was turned into a woman with low IQ to keep him from continuing his rebel activity.
Sadly, I don't remember much else - it's only the weird (and probably quite sexist) stuff that stuck to my head.
The story is, I assume, from the 80s or early 90s.
I put some further thought into the publication date, and I'd focus on late 1980's to 1995 by now.
The book was from a public library, and they seem to have put mostly pretty current stuff on their shelves, such as A Song of Ice and Fire, When Gravity Fails and so on. Some older classics like Asimov and Lem, but the majority apparently was newer.
Common sense would say that it was something pretty popular or well-known, as most of the stuff I remember from that shelf is seen as a classic now. But I just cannot find that one now.
One younger guy was kind of a soldier or lieutenant in what I remember as the rebel organization. He was a point of view character iirc. He got captured by the enemy or messed up something, and as a punishment (again: probably sexist to current standards) was turned into a female waist-down. He hid that from others, but had trouble riding a horse with his changed body for whatever reason.
Another older guy was the organization's leader, guru or something similar. He was known to be a smart, sly tactician, hard to catch, never giving up - a kind of old fox stereotype. He was captured by the enemy (that seems to a common theme) and turned into a full-fledged woman, or what stereotypical parody the author thought women are. He was dumbed down on purpose and given an unnatural appetite for sexual intercourse, both to make him unable to continue his war effort. He did conquer those problems, however, and somehow contributed to the rebellion later on.
That does sound vaguely similar to Medusa: A Tiger by the Tail from Jack L. Chalker, but I don't think it was that book, judging from the plot summary on Wikipedia.