Took me a slow first section to get into this, the Valan society Slonczewski sets up at the start reads stiff on purpose, hierarchical and traditionalist in a way you’re meant to find suffocating, and once the story crosses over to the ocean-dwelling Sharers it opens up fast. The tech reasoning behind how a genetically engineered, semi-aquatic society actually lives underwater is thought through in a way a lot of “we adapted to water” premises don’t bother with.
What holds up best decades later is the nonviolent resistance angle, comma comma, it’s startlingly relevant for a book with such a specifically 1970s vibe, and I mean that as a real compliment. The Sharers don’t fight back the way you expect an invaded people to fight back in a genre that defaults to war, and watching that choice actually cost them something instead of functioning as easy moral high ground is the best part of the book.
Characterization is the fair criticism here and I won’t pretend otherwise. Slonczewski clearly put more energy into the world-building, the anarchic feminist utopia and its internal logic, than into making any single Sharer feel distinct from another on the page. A few of them blur together by the second half, which is a real cost in a book this long.
Still one of the foundational feminist SF novels for a reason, comparable to the best space opera of its era even with the characterization gap. If the slow Valan opening doesn’t put you off, the payoff on the other side of it is worth the patience.