Iain Banks is great SF The Culture novels in particular.

They all have dark elements but Use Of Weapons especially so. Look to Windward is my favourite, but I would not suggest reading it first. Player of Games is a good entry point into The Culture universe.

Darth bane triligy starting with Path of destruction

Joe Abercrombie, The First Law Trilogy

You like Stephenson? What about William Gibson? Seems like you woud have already read most of it, but just in case…

Most Cyberpunk, classic even, his first: The Sprawl Trilogy
Great move from the farther future, hard cyberpunk to day-after-tomorrow (maybe my favourite): The Bridge Trilogy
Even more to the today/tomorrow feel, but maybe a steep hill to climb without following his previous “evolution” : Blue Ant Trilogy

Connie Willis’s Oxford Time Travel books!! Lighter in tone than what you are referring to, but often compelling. There is an order to the stories, but it’s not vital, really. With Three free books I would suggest “To Say Nothing About the Dog”, then “Blackout” and it’s continuation “All Clear”.

“Lovecraft Country” and “Destroyer of Worlds” are a pair that focus on a black family’s experience of late 50s/early 60s (can’t remember) Sorcery in the U.S.

Stand alones? Have you read “Project Hail Mary”? Great bit of non-sequential storytelling as the narrator regains his memory and figures out where he is and why. Avoid spoilers, even synopses for this one for maximum effect. A.G. Riddle’s “Lost in Time” was a balance of whodoneit and time travel that I found enjoyable.

Ooh, check out N.K. Jemisin’s “The Broken Earth” trilogy.

The story opens with a cataclysmic event followed by shifts in how it’s narrated that sometimes results in brutal circumstances being treated with a jarring casualness. And while there is a lot of worldbuilding at the beginning of the first book, I thought it made sense pretty quickly and I suddenly found myself in a world of survival and power struggles. Add in a magical ability to manipulate the earth and it’s an incredible fantasy series.

It is dark and grim and unpredictable. It mixes unspeakable cruelty with moments of brilliant kindness. The characters are complex and so beautiful connected.

…I think I need to go read this series again. I had almost forgotten how much I love it!

Travis Baldree is a really great narrator, but I’m not sure what he’s narrated that’s dark/grimdark. He does mostly fantasy.

If you haven’t checked out Ursula K. Le Guin, I highly recommend her. Lathe of Heaven is a great/short taste of her style, but if you want something darker I’d say maybe The Eye of the Heron.

I would recommend the classic Asimov series, Foundation. It’s a post major galactic society. It’s not much on cyber, computers were not a thing when it was written. But in replacement of that, everything nuclear is cool and amazing.

Trigger Warning by Neil Gaiman. A collection of short stories but they’re rather dark and many interesting ideas in there.

One of my favourite “reads” on a particularly late night drive up to Edinburgh that still sticks with me nearly 10 years later.

The Spear Cuts Through Water by Simon Jimenez is wonderfully read by Joel de la Fuente and it’s a really special book.

• The Gilded Ones by Namina Forna; fantasy series

• Black Sun by Rebecca Roanhorse; fantasy series

• Oryx And Crake by Margaret Atwood; post apocalyptic series

• Lilith’s Brood by Octavia Butler; gritty sci-fi series

• Wild Seed by Octavia Butler; the first of the Patternmaster series, gritty sc-fi

Give GraphicAudio a try. They do professional full cast audio productions of novels/series.

Some series that i have tried and enjoyed:

• The Demon Wars Saga
• The Forest Kingdom Saga
• The Night Angel Trilogy
• The Serrano Legacy
• Vatta’s War