I recently remembered reading a soft sci-fi novel about 10-15 years ago (borrowed from a library); the basic premise was of some space empire (based throughout the Solar System I believe, but primarily in Space rather than on planets, moons, etc.). Most people I believe lived on some kind of ring (Dyson-like maybe?), and there was matter replication-like capabilities and teleportation.
The Empire was ruled by a young (possibly eternal) Empress, with the protagonist being a male friend of hers (possibly an artist) who may have been in a relationship with her (possibly before she became Empress?). She somehow controlled all the technology (nanites?) which allowed people to do as they wished. The ending featured her being assassinated, but "surviving" by using the teleporters to duplicate herself so she could be with the protagonist.
I think the book had a title of something like "Singularity".
Does this ring a bell?