You can check out her screenwriting credits if you like, it is an impressive body of work. But her admission to the ranks of Appendix N luminaries is due to her Sword and Planet novels, stories owing a lot, I think, to Edgar Rice Burroughs’ “John Carter of Mars” and “Carson of Venus” stories, and sharing the same branch of the literary family tree as C.L. Moore’s “Northwest Smith.”
Brackett’s Eric John Stark stories are pulpy sword and sorcery set on planets near and far, her Mars a desiccated world of lost civilizations and ancient races lingering on the edge of extinction. It can be fun stuff, though her tales have a tendency towards the grim, especially the “Skaith” books – litanies of unpleasantness that can wear on the reader.
It’s a toss up which I enjoyed more, the Eric John Stark outing “Outlaw of Mars” or “The Sword of Rhiannon” also set on Mars but featuring Matthew Carse as the main character. I can see either of them inspiring Mr. Gygax.
She’s inspired me as well. Perhaps you’ll see the result of that inspiration soon.