Pandora’s Star (Commonwealth Saga) by Peter F. Hamilton

In AD 2329, humanity has colonised over four hundred planets, all of them interlinked by wormholes. With Earth at its centre, the Intersolar Commonwealth now occupies a sphere of space approximately four hundred light years across.

When an astronomer on the outermost world of Gralmond, observes a star 2000 light years distant – and then a neighbouring one – vanish, it is time for the Commonwealth to discover what happened to them. For what if their disappearance indicates some kind of galactic conflict? Since a conventional wormhole cannot be used to reach these vanished stars, for the first time humans need to build a faster-than-light starship, the Second Chance. But it arrives to find each ‘vanished’ star encased in a giant force field — and within one of them resides a massive alien civilisation.