Used book – La mécanique du talion, Laurent Genefort

His name was Kovall. They tortured him beyond all pain. Yet he survived. He rebuilt himself. But Kovall is dead; now here is Valrin, and the hunt begins. To understand and, above all, to exact revenge. What does the enemy's power matter? Valrin will not give up. From planet to asteroid, from ship to arcology, he gradually follows the trail of a cosmic conspiracy whose stake is nothing less than the domination of the Galaxy.