Angelmass

Angelmass, a black hole deep in space, emits "angels," small particles that render humans calm, reasonable, and virtually incapable of lying. The Empyrean, human colonies in the far reaches of the galaxy, has discovered the angels and the power they wield. All members of Empyrean government must carry an angel.
The Earth-based Empire, the Pax, view the angels as an alien plot to subvert humanity. They dispatch Jereko Kosta, an innocent academic, to spy on the Empyrean and find out the truth about angels. With Chandris, a grifter who dogs his steps, he enlists on an "angel-hunting" ship. Close up, Kostas learns the angels may be more dangerous than the Pax fear.
Before he can react, the Pax dispatches their most powerful warship to confront the Empyrean. Now, Kosta and Chandris, among the few who know the truth about the angels, stand between the Empyrean, the Pax, and war.