I really liked Adrian Tchaikovsky's stuff. Particularily "Children of Time" and a lot of his standalone novels like "Alien Clay", "Shroud", and "Service Model".

Another good book that explores truly alien aliens is "A Fire Upon the Deep" by Vernor Vinge. I really like how a lot of concepts are presented in a way that initially lets you sort of figure out whats going on before too much exposition is used to clarify alien ideas.

Finally, I need to recommend David Brin's books, like the uplift trilogies or oven his weirder stuff like Kiln People. He does a good job of establishing a technology or social convention and building a world around it.

Alistair Reynolds' Revelation Space series is excellent. My introduction/entry point was "Chasm City," and that played out awesomely for getting into the first two novels in the formal trilogy. Reynolds was also partially inspired by the Culture series.

It’s hard to beat the Culture series. While not quite the same I found that Ken MacLeod’s Engines of Light Trilogy and Ursula LeGuin’s Hanish Cycle books were both excellent in their own ways and hit a lot of similar notes.

Foundation is a good series in a similar vein. But I agree with artifex. Nothing really beats The Culture.

Richard Morgan's Altered Carbon, Broken Angels and Woken Furies.

Anything from Peter F Hamilton's Commonwealth saga.

The Saga of Seven Suns by Kevin J Anderson.

I'll think of more.

The closest I have found is Neal Asher's Polity books. I like Asher even more, if they are a bit darker. I can't recommend them enough.

I enjoyed Cixin Liu's Rememberance of Earth's Past trilogy (Three Body Problem, The Dark Forest, and Death's End).

The Xeelee series is pretty great if you're looking for another multi-book commitment

Which novel was your favorite?

Kim Stanley Robinson's Mars series is pretty good.