I just finished reading Incandescence by Greg Egan.
As always, Egan writes with his hard-core knowledge of physics. You simply can't expect to understand everything unless you're really enjoying that third year degree subject right now. The core part of this book is about a pre-industrial race working out some of the details of the theory of relativity from observation and low-tech experiment.
It really is very cool. The other half of the book fills in some culture and technology for the rest of the galaxy, and could probably be an interesting backdrop for many SF novels, but that isn't how Egan works. The contrast between the halves is stark, and you are left wondering how that will be resolved right up until the end. Which I won't tell you about except to say I didn't find it very fulfilling.