Spy for a Dead Empire (The Adventures of Grant Scotland, Book One). The Adventures of Grant Scotland, #1

AELFA, THE GRAND CAPITAL of the once mighty Aelfan Empire, has fallen. Barbarian leaders now inhabit her buildings and attempt to ape her customs. Meanwhile, war parties and nomadic tribes still harass her broken legions across the shattered remains of her once rich lands. All that stands against them now is the city of Zyren, the last bastion of Aelfan rule. But at least one man in the captured city stands with Zyren, too.
Grant Scotland, a man leading a double life because his own had been taken away from him by the very people he served. An unwilling recruit into the business of clandestine missions and deceit, he searches for anything real to cling to as the world around him devolves into insanity. And when an old friend shows up asking Grant to help save his family by delivering a mysterious book to a shadowy figure, Grant's two lives collide and he is thrust into an even stranger world than he had known; one where ancient magic is wielded by deadly players who compete against one another for a prize greater than simply the rotting carcass of a dead empire.