In the Mouth of the Whale by Paul McAuley

In the Mouth of the Whale by Paul McAuley is set in the Quiet War universe. I thought it was the 3rd book in the series but it is, apparently, a standalone novel. A thousand years after the Quiet War mankind has moved from the outer planets to new star systems.

Three varieties of post-humans, Ghosts, Quicks, and Trues, seek their destiny in the Fomalhaut system while a human from the far past is on its way to change everything.

The plight of the Quick, the decadence of the 'originalist' Trues, and the aberrational Ghosts are all portrayed with great imagination and verisimilitude. The fantastical settings of Fomalhaut are nicely set off against the 'flashbacks' to pre-Quiet War Earth. Again, though, some of the descriptions of planetary settings go on for so long in detail that they are impossible to picture.

The three interwoven plot lines combine in the end in a neat conclusion. McAuley finds the right balance between rich futurist speculation and action-adventure with compelling ethical issues.

The '3rd book' in the series, Evening's Empires comes out in 2013. Myself, I'd call this the fourth book and read In the Mouth of the Whale after The Quiet War and  Gardens of the Sun.