The Lord of Worlds by Tom Pugh
Europe has closed her doors to English goods. Desperate to find new markets, Queen Elizabeth's head of intelligence sends exiled soldier Matthew Longstaff east to start negotiations with the Ottoman Empire. Accompanied by his wife Aurélie, Longstaff arrives in a city unlike any he's known before - an absolute monarchy without an aristocracy; an Empire governed by slaves, a system powered by jihad and uniquely tolerant of religious minorities.
The city is enchanting - and Longstaff's mission impossible. Starved of resources, he finds himself drawn into a game of piracy and blackmail. A trade agreement lies within his grasp when suddenly the stakes are raised again. A greater prize now tantalises - one with the power to change the world forever.
But time is running out. As Longstaff's enemies pursue him relentlessly though the streets and palaces of Istanbul, it will take all his strength - and all Aurélie's cunning - to secure his prize and escape the Lord of Worlds.