Stephen King's"Different Seasons" has 4 great novellas in it.
3 were made into movies.

I did an entire semester of independent study on novellas when I was in grad school.

Favorites:
Jacob's Room / Virginia Woolf
Breakfast at Tiffany's / Truman Capote (so different from the movie and much better)
The Dead / James Joyce
Bartleby, the Scrivener / Herman Melville (hilarious)
Brokeback Mountain / Annie Proux

Murderbot is universally beloved. Second that suggestion!

Thornhedge by T. Kingfisher (Fantasy)
https://www.goodreads.com/book/show/61884932-thornhedge

A Matter of Class by Mary Balogh (Historical Romance)
https://www.goodreads.com/book/show/6440767-a-matter-of-class


I haven't read this, but it's getting a ton of attention:
Haunt Sweet Home by Sarah Pinsker
https://www.goodreads.com/book/show/203579272-haunt-sweet-home

There's a goodreads list for literally everything. Just search...
https://www.goodreads.com/genres/novella
https://www.goodreads.com/list/show/1236.World_s_Greatest_Novellas

A River Runs Through It

All Systems Red by Martha Wells - book 1 in Muderbot series.

Claire Keegan's work, not necessarily novella, more like long short story, but near enough and all brilliant:

Foster
Small Things Like These
So Late in the Day

Psalm for the Wild Built

The Uncommon Reader

84, Charing Cross

Looking for novella length book suggestions. (fiction or non-fiction)