Order of the Sun - The Order Trilogy, #1

An undercover mission is the worst place to find love. Lord Cerrick Montef has been many things: an unloved son, a criminal in a powerful gang, and a royal spy for a man who would fire him if he knew of Cerrick's unsavory past. When Cerrick's boss sends him abroad, alone, and undercover on his latest investigative mission, he must adopt a new role: the husband of a foreign prince. The arranged marriage to Prince Njord is strictly business that will end once Cerrick closes his investigation.
Yet Njord is nothing like he expected: kind and genuine and handsome. As Cerrick struggles with deceiving Njord, he uncovers a conspiracy that makes him question his boss, his country, and himself.