I posted this comment on a similar topic a while ago, for context it was replying to someone who wanted to pick 2 LeGuin novels to read to essentially get a survey of her work. I've liked her standalone novels as well, but I see them get less discussion generally. I think her work that I see referenced most often is the short story The Ones Who Walk Away from Omelas.

LeGuin is one of my favorite authors. I've read a lot, but not all of LeGuin's novels. She has 2 main multibook series that I've read, the Earthsea books and the Hainish cycle.

Earthsea is sort of YA fantasy, but grows up throughout the series. The first 3 are a self contained trilogy, and my favorite is Tombs of Atuan which is book 2, I think would be okay as a standalone title. My other favorite is Tales from Earthsea which is book 5, and is a collection of short stories set in the setting. You'd be missing a little context only reading Tales, but this could also be a standalone.

The Hainish cycle is scifi, and are only loosely connected by the setting and don't have a too firmly established chronology, or any shared main characters. My favorite from the Hainish Cycle is The Left Hand of Darkness and my 2nd favorite is The Dispossessed.