Paul McAuley 
Eternal Light [EPUB ebook] 

In the aftermath of an interstellar war an enigmatic star is discovered, travelling towards the Solar System from the galactic core. Its appearance adds a new and dangerous factor in the turbulent politics of the inhabited worlds as the rival factions – the power-holders of the Re United Nations, the rebels who secretly oppose their power, and the Religious Witnesses – all see advantages to be gained. But what awesome technology started the star on its journey half a million years ago – and why?