Strange i always thought it was credited to both since the name Ilona Andrews is actually a combination of both her and her husbands name and their pretty open on their website about it being a joint authorship. At any rate Kate Daniels is a great series and the character arc that kate undergoes over the course of the books is wonderful but thats just mho. The vampires that inhabit Kate's world certainly are an interesting interpretion.
The Mercy Thompson series, which i noticed is on your to read list, also features non stereotypical vampires (as in their not suave vampire diaries/true blood vamps) but their not as creepy as the ones in the Kate Daniels series.
I hope you enjoy both those series as they are great imho