The Moon and the Sun by Vonda N. McIntyre

The Moon and the Sun won a Nebula and was up for the Tiptree and Locus awards.

Father Yves de la Croix--Jesuit priest, natural philosopher, and explorer--has returned to King Louis XIV bearing a gift of two sea monsters: one alive, one dead. Little by little, Yves does the autopsy with the assistance of his sister, Mademoiselle Marie-Josèphe de la Croix.

Marie tries to train or domesticate the sea monster as a pet, but slowly learns that there is more to the sea monster than she first supposed.

Eventually they communicate, and Marie gets a fuller understanding of this race or species. Unfortunately, the sea monster's flesh is rumored to give immortality, so they want to dine on its flesh. Marie has to come up with a way to prevent this.

Minor spoilers:

The main plot could be guessed as soon as the conflict is established. Of course, humans once again underestimate another species. The victims must be rescued. In fact, much of the basic scenario mirrors Guillermo del Toro's The Shape of Water: the capture and abuse of, and experimentation on a humanoid sea creature.

The sea "monster's" name is Sherzad--a nifty nod to 1,001 Arabian Nights. After all, Sherzad (like Scheherazade) has a story to tell to save her own life.

The first two-thirds is well written but pales in comparison to the last third except for the scene establishing communication and the autopsy which is a well-sketched painful moment. The real power comes in the last third when the court intrigue unfolds, and we learn more about this sea-person.

The speculation is rather limited, so maybe it is like LeGuin suggests above the illustration that this is an alternate history. Apparently, McIntyre did much research to capture the period, and it was convincingly captured. A historian might need to explain the departures and their ramifications.  I'm just a science dude.

When word got around Vonda N. McIntyre was ill, I decided to pull down this novel and give it a read. If I have McIntyre's ordering right, the novel began as a faux encyclopedia article, which she had to restrain from becoming a story with characters.

She took a script-writing class and wrote an earlier version of this story, which she later expanded into a novel. However, publishers move faster than the movie industry, apparently, and she published her novel well before they started shooting. The movie, starring Pierce Brosnan, has been filmed but remains unreleased pending special effects, four years later.

Maybe something went wrong elsewhere, but you'd think they'd try to recoup some financial losses by releasing it as straight-to-video, or have a limited release first. Surely, book fans would flock.

UPDATE: The movie was just released. See discussion here.