Consider Phlebas

I was torn between giving 3 or 4 stars. It's a good book with solid world-building (with enough left for the reader to figure out between the lines) and a decent plot. However, I felt the characters were a bit weak, with really weak motivations behind their actions. For presumably galactic civilisations, you would assume there would be a bit more nuance behind their actions, but that wasn't the case.

That said, I gave 4 stars not because of that but rather because the ending happened way too quickly, and it wasn't clear to me what the crescendo in the last 1/3rd of the book was building towards. Overall, a great book and my opinion might change once I finish the whole series.