Of what others have suggested and that I’ve read: the ones most similar to what you’ve finished are:

• The First Law series by Joe Abercrombie
• The Expanse series by James SA Corey
• Hyperion (at least the first two books, w/ optional two more) by Dan Simmons

New recommendations:

• Dhalgren by Samuel R Delany (content warning)
• The Baroque Cycle series by Neal Stephenson (Snow Crash and the Diamond Age may both be better starting points for the author, but may fit your other criteria less)
• The Book of the New Sun series by Gene Wolfe

Other works that stretch your genre boundary but may evoke the right emotion:

• Collected Fictions by Jorge Luis Borges
• If on a Winter’s Night a Traveler by Italo Calvino
• The Name of the Rose by Umberto Eco
• Cloud Atlas by David Mitchell
• The Satanic Verses by Salman Rushdie
• Lovecraft Country by Matt Ruff
• Plain Bad Heroines by Emily M Danforth
• John Dies at the End by David Wong

I haven’t seen Project Hail Mary by Andy Weir here. It’s Sci-Fi, it might not be very sanderlanchey but it’s one of my favorites. I read it in a weekend, and it usually takes me 1-2 weeks to read a single book. I gripped me from start to finish, and had a great conclusion. I recommend you give it a try!

Some of my favorites! Mostly Sci-fi, but there a bit of fantasy too! The starred items are my absolute favorites; listened to on repeat. Not the most obscure list, but I don’t care.

The Expanse series is my favorite, but I want to highlight Dungeon Crawler Carl and Redshirts. Sci-fi tends to be serious and depressing, but these books are funny. I genuinely laugh out loud at Dungeon Crawler Carl.

• Leviathan Wakes by James SA Corey*
• Red Rising by Pierce Brown*
• Old Man’s War by John Scalzi
• Redshirts by John Scalzi
• Hyperion by Dan Simmons
• Ancillary Justice by Ann Leckie*
• The Midnight Library by Matt Haig*
• Wool by Hugh Howey
• Heretical Fishing by Haylock Jobson
• Dungeon Crawler Carl by Matt Dinnimon, narrated by Jeff Hays (listen to the audio book. It’s good in its own, but the narrator goes above and beyond anything else I’ve ever heard)*

I’ll recommend some from the lesser known progression fantasy genre:

• Cradle by Will Wight
• Mage Errant by John Bierce
• Mother of Learning by Nobody103 (Domagoj Kurmaić)
• The Weirkey Chronicles by Sarah Lin
• Beware of Chicken by CasualFarmer
• Super Powereds by Drew Hayes

A couple of my favorites from recent years, as someone who has also read all of the Cosmere books.

The Broken Earth trilogy, starting with The Fifth Season

The Between Earth and Sky trilogy

Two very different recommendations.

First is the Southern Reach novels by Jeff VanderMeer (the first one being Annihilation). Unsettling, surreal Lovecraftian sci-fi. Gorgeously written, beautiful prose, and very memorable.

Second is the Mars Trilogy by Kim Stanley Robinson (starting with Red Mars). Hard sci-fi on an almost unprecedented scale: a comprehensive and incredibly detailed narrative of the colonisation of Mars, which covers almost every possible aspect of the story in glorious, engaging detail. You get everything from the love triangles and personal rivalries of the colonists, to politics and religion, to macro-economics, to superstructure engineering, to long deep chapters covering hydrology, micro-biology, the finer points of lichens and mosses, to architecture, art… Honestly, it’s breathtaking in just how thoroughly it covers its subject whilst still being a poignant, engaging, story. Not to everyone’s tastes, but it could certainly make an impact.

Yet again I will pitch for Piranesi. My favorite book of recent years.

It sounds like you’re looking for a mind blowing sander-lanche.

I’d highly recommend going through Ted Chiang’s book “exhalation”. A more popular example of his work is the movie “arrival”, which was based on one of Ted Chiang’s short stories.

It’s a collection of short stories, but don’t be misled - these stories have stuck with me for years, and as someone who has also read all of the cosmere, it is these short stories that have the biggest twists, and also the largest impact. A few of my favorites are below:

I’ve always wondered to myself, "how many of my youngest memories are my own, and how many are in reality, stories told around photos that I’ve seen? The story “The truth of fact, the truth of feeling” makes you think about the role of technology in our memories through one example in the past, and one proposed in our future.

“What’s expected of us”, free on Nature, is a haunting story going over the role of free will that can be read during a bathroom break.

Finally, “anxiety is the dizziness of freedom” had one of the biggest gut punches I’ve ever read. One best gone in blind, I think.

My absolute all time favourite sci-fi book series is John Scalzi’s “Old Man’s War”.

I can’t recommend this book series enough. Kept me up several nights because I couldn’t stop reading (and suffered for it at work).

Scalzi added a lot of humor too and it’s brilliant.

The Malazan Book of the Fallen, by Steven Erikson.

Ten brick-thick volumes that will alternately fill your heart to bursting then stomp on it until you’re wrung out like a rag. It is one HELL of a ride. It does have a steep immersion curve, so be prepared to take a couple of attempts to finish the first one.

When you find yourself laughing at the tragedy and crying at the jokes, you’ll know.

Also, the Locked Tomb series by Tamsyn Muir. Adorkable romance, badass as hell, will break you. Gets increasingly weird as it goes along. Is good, has massive cult following.

And by no means least, the Machineries of Empire series by Yoon Ha Lee. Ostensibly weird Korean military space opera, but with a real gut punch; you won’t forget this one.

The Wayfarers series by Becky Chambers is some of the best sci-fi ever written, in my opinion. Deals with high stakes stuff but has such a gorgeous focus on characters and cultures. I could just live in some of the moments in those books.

Going back to the 80s here, but I would recommend the Taltos series by Steven Brust. It’s a very catchy read, great world-building. It starts as pretty much hard-boiled hitman whodunit in a fantasy setting, but escalated to much higher stakes. He’s still writing the series.

Brusts other stuff is good too.

I second the other suggestion in this thread of Becky Chambers’, classy stuff that really draws you in, very cozy, but not epic sci fi!

The other series I’d recommended then is an old one by Greg Bear: The Way series, starting with Eon. It is about an asteroid which appears in orbit when Earth is at the brink of war, and is one of the most mind-bending, far-fetched sci-fi stories I’ve read, that is still arguably hard sci-fi.

1. Realm of the Elderlings saga by Robin Hobb (completed I think)
2. World of the Five Gods series by Lois McMaster Bujold (ongoing)
3. Wall of Night series by Helen Lowe (ongoing, link goes to first book in the series)
4. Innsmouth Legacy series by Ruthanna Emrys (ongoing, link goes to the first book in the series)
5. Piranesi by Susannah Clarke (standalone, not a series)

I’m usually a SF guy but the most memorable read these past ~2 years was the fantasy books The First Law by Joe Abercrombie. The first book hooked me in and I ended up devouring all 9 books. The audiobook version read by Steven Pacey was superb, that man really breathed life into the characters and I’m glad I listened rather than read them.

I recall wanting to read more dark fantasy after and tried listening to Stormlight Archives on recommendation from a friend but the readers and writing was so bad in comparison I gave up after 2 hours.

It’s an old four book series from the '90s but I would recommend The Saga of Pliocene Exile by Julian May. They’re available as ebooks. The first one is called The Many Coloured Land.

If you enjoy the world-building, Mrs May wrote a companion series which, IMO, is even better! Starting with a link book (Intervention) there is a three book series called The Galactic Milieu series.

Both series mix fantasy and sci-fi and are truly excellent reads.