Zero World By Jason M. Hough

In the near future, technologically enhanced superspy Peter Caswell is dispatched on a top-secret assignment unlike any he's ever faced. A spacecraft that vanished years ago has been found, along with the bodies of its murdered crew-save one. Peter's mission is to find the missing crew member, who fled through what appears to be a tear in the very fabric of space. Through this mysterious wormhole lies an even more confounding reality: a world that seems to be Earth's twin.