You could finish the rest of the enders game universe, it's a really interesting read

While i havent finished them, i really enjoyed going through the Battletech novels.

Big stompy robots in a galaxy spanning civilization with a nice long history. The books take place over a few generations so as you read you get interested in the events from previous books by different factions in universe. I also like that there are a variety of authors so you dont get fatigued by a single style.(at least that was my experience)

Lots of intrigue and conflict with enduring characters.

The Empress of Salt and Fortune https://g.co/kgs/dFcR5h

Mix old school yakuza family drama with a hint of mystical powers that grant the characters certain physical/mental enhancements and you get The Green Bone Saga Trilogy. Very good series I couldn't put down.

If you're looking for something longer, try Brandon Sanderson's cosmere (start with either Mistborn or Stormlight Archives.)

Or perhaps Jim Butcher's Dresden Files (hard-boiled detective who also happens to be a wizard.) First few books are a bit weak, but gets much better.

Some other ideas:

Murderbot Diaries, The Locked Tomb, Assasin's Apprentice, Broken Earth, Kings of the Wyld.

I have recently started Sons Of Ares by Pierce Brown, Starting with Red Rising.

It's very good so far. It's a bit enders game ish with some grand politics like game of Thrones and imo elements from expanse.

Essentially it's humanity have populated all the planets and moons in our solar system and through body modification created specialized color based races to do everything. And ruled by the Gold's

It is a YA but fairly gritty and it never really goes where I expect it so I'm consistently entertained. It's well written.

The Long Way to a Small, Angry Planet by Becky Chambers, if you want another addition to the Sci-Fi theme.

Can also second some books others have mentioned, like Dune (one of my all-time favorites) and Three Body Problem (for a recent one I liked, although it was a bit "rough" in terms of style and storytelling).

Neal Stephenson has a few good SF books (seveneves comes to mind) and some good alt history (cryptonomicon).

I just finished re-reading the three body problem series and it's still good too.

Sounds like you have a lot in common with my father's reading tastes. In which case, I will recommend the Thursday Next series by Jasper Fforde.

The Stone and the Flute by Hans Bemmann

One of the most profound set of allegories I've ever read.

If you like DnD type stuff, He Who Fights With Monsters is about a dude who wakes up in an alternate universe where magic is real. It's pretty great, and 10 books deep.

Spiral Wars series by Joel Shepherd.

Bit more action-adventure based, but good fun read with good characters and worldbuilding.

If you enjoyed the mystery part of the expanse I recommend Beacon 23.

You like many of the same books that I like. Try the Red Rising series by Pierce Brown. I just read it recently and now it’s one of my favorites.

For sci-fi, one I haven't seen mentioned here yet is Red Rising.

Kind of an Enders Game meets Hunger Games in the first book, but quickly expands into a solar-system wide war with lots of intrigue, star-wars-like tech, and amazing characters.