The curse of Chalion

We follow a noble soldier who's coming back to his land after having had a hard time on a galley in a foreign land. 
He finds a job at a noble woman's house as the tutor of her grand-daughter. We learn that he was betrayed by the prime minister - because of something that he knows about the prime minister's brother. 
He has to follow the heiress and her brother the heir to the capital city, as the brother is the next in line and the current king wants to groom him for the position. 
Once in the capital, our hero sees that the brother of the prime minister is playing cosy with the heir and flirts a bit with the heiress. 
They learn that this man, the prime minister brother, is bound to be the heiress future husband, and nobody wants that.  
The king is manipulated by the prime minister. So our hero tries some dark magic that is meant to kill the groom and himself - as a payment to the killer demon. 
The brother dies, but not our hero, instead he find to host the demon and the soul of the brother in his body. And he becomes some kind of blessed person who can see curses and who are the other saints. 
The religion is based on 5 people, the father, the mother, daughter, the son and the bastard. 
He finds a suitable suitor for the heiress, saves the heir and the curse that is upon every kings, by kinda dying three times. 

It's funny, as I read it I thought not much is happening and it is a bit boring, but writing the synopsis I find that there was also a lot to be said. 
It read well, but the world felt kinda empty -- what made it fantasy was the religion that didn't impact many people, and the nobility titles.