I'm on book 6 of the Expanse and love it! My suggestions:

The Culture series - Iain M Banks. Space opera that gave us luxury gay space communism. You can pick up any book as a starting point - they're set in the same universe spanning millennia and have very little interconnection. Explores themes of humanity in an AI world (choice, war, deceit, love, etc)

Revelation Space series - Alastair Reynolds. Closest in terms of style and sweeping scope to The Expanse. Same dry humour that can get a bit much at times.

Three Body Problem trilogy - Liu Cixin. Leans a lot heavier into the Science of sci-fi and can be very dense, but one of my favourite trilogies. What happens when you finally get a signal back from space?

Monk & Robot series (novellas) - Becky Chambers. Pure hope punk and absolutely delightful (without any of the incredibly distateful and harmful tropes found in Midnight Library). There are only two out so far, and you'll be able to read them in a day. Of all of the recommendations I've listed, I implore you to read this one.