The Iron Tactician by Alastair Reynolds

In a universe ravaged by endless war, a spacefaring adventurer named Merlin embarks on a quest to locate a mythical weapon that could turn the tide of conflict. As he navigates through the remnants of a once-great civilization, Merlin encounters a derelict spaceship harboring secrets from the past. With the help of a resourceful AI and a mysterious woman, he delves into the ship's history, uncovering truths that challenge his understanding of the war and his own purpose. The journey becomes a race against time as alliances shift and hidden agendas threaten to derail his mission.