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.