Wow, very very nice...
I am not aware of the Iron Druid Chronicles (hey, I'm new to this site, as well as to fantasy as a genre ) but the drawing is really good.
I would agree with DragonOfTheAerie in regards to making the guy a bit more dynamic. Moreover, the way he's petting the dog, it looks more like he's holding the dog back (as if he's holding the dog's forehead so that the dog won't move forward) instead of actually petting him. If he's petting him, his hand would probably slide more backwards, so maybe only the thumb of his hand will be visible from the front.
..Actually, our hands move back and forth while petting an animal anyway, but I believe if you placed his hand a bit more to the back, it will be easier to understand and more appealing to the eye.
Also, that is a big dog, right? xD
I am not aware of the story or the world, as I mentioned before, but the dog looks quite big compared to the human (I know there are such dog breeds, but I just wanna make sure ).