I didn't really get where the AUness of this AU comes from and I have no idea about The Dresden Files but I enjoyed the story: the mystery, the sex (wonderful and not romanticised), the storytelling manner, the magical/Muggle stuff, ghost!Snape who liked to watch and eavesdrop :). Thank you very much!
PS: there are a couple of things you might want to fix when you repost it. A few commas as address separators are missing in a place where they change the meaning ("Oh, I'm sure you are Malfoy." and a couple more). And this thing: "and without the ability to cast an Expecto Patronum" -- it should be "Patronus charm" 'cos Expecto Patronum is the incantation, I'm calling a protector. But that's nitpicking a willing perfection on a good thing :)