Commonwealth Saga #2: Judas Unchained by Peter F. Hamilton

In the star-spanning civilization known as the Intersolar Commonwealth, twenty-three planets have fallen victim to the Prime, a technologically advanced alien species genetically hardwired to exterminate all other forms of life. But the Prime is not the only threat. The Starflyer, an alien with mind-control abilities impossible to detect or resist, has secretly infiltrated the Commonwealth and is sabotaging the war effort. Is the Starflyer an ally of the Prime, or has it orchestrated a fight to the death between the two species for its own advantage? Caught between two deadly enemies, the fractious Commonwealth must unite as never before. This will be humanity’s finest hour—or its last gasp.