With Resplendent, Baxter does for his Destiny's Children saga what Vacuum Diagrams did to his Xeelee Sequence. Both these books provide more detail, fill in gaps, and generally expand on the universes Baxter has created.
Both the Xeelee sequence and the Destiny's Children saga occur in the same universe, one where humanity has all but conquered the galaxy, and is in the midst of war with a seemingly all-powerful alien species, the Xeelee.
Resplendent contains stories ranging from humanity's occupation at the hands of (another) alien species, the Qax, to humanity's domination of the galaxy.
This is definitely a must have for any reader of the Destiny's Children saga!