Stephen Graham Jones, The Bird is Gone. Alt future/history specfic in which the Dakotas have been returned to Indian control. I fricking ADORE the worldbuilding in here. The worldbuilding shown within the main narrative makes me howl with laughter -- when I finally caught on to what "pinkeye being all the rage" is about, I laughed and laughed and laughed. But! And! There is also a glossary in the back, the entries of which contain lots of references to the alt-history that became this alt-future: I would so, so, so adore to see some of these stories fleshed out in fic! Pleasepleasepleasepleaseplease.

(Should I be rec'ing Cynthia Leitich Smith's Tantalize/Eternal/Blessed series here? YA vampire/goth/werewolves. Muscogee author, some of the main characters are POC, but the content is not explicitly First Nations.)

Joseph Bruchac! Fantasy and horror and historical fiction, most for YA and MG audiences.

And Thomas King! Thomaskingthomaskingthomasing! There's the Medicine River series of novels (Yay, Harlen Bigbear!), plus marvelously surrealistic short stories (some of which are fandomy themselves!), plus the children's books (Coyote Columbus Story!).