Double the Risk by Samantha Cato. Two cops–partners–fall for the new medical examiner. Nice bonus ATM–series is about a family of cops trying to expose corruption in the Boston PD. (CN for the rest of the series–the 3rd book has some heavy transphobia.)
The Moon is a Harsh Mistress by Robert Heinlein. Polyamory classic.
After You by Ophelia Bell. I’m iffy on this one. Short story, three-way sex, established couple has a three-way with someone they are both attracted to. Normally I wouldn’t tag it polyam, but reviewers say the story ends with all three in love with each other. And Bell has written at least on other polyam story (Dragon’s Melody).
The Fifth Sacred Thing by Starhawk. Post apocalyptic story with both utopian and dystopian societies. On the Goodreads Polyamory in Fiction list and has Hispanic characters.
Mother of Demons by Eric Flint. Polyam relationship is very much in the background, but it’s there.
The Allison Dutch Series by Michon Neal. And many of Michon’s other books.