Its not often you can get to book 6 and feel you've barely scratched the surface of the characters, plot etc. yet still finish the book in one sitting. This is one of those series that just seems to gain in breadth and skill. As there's no write up i'll give a quick overview:
Harry Dresden is Chicago's only practicing wizard investigator and is listed in the yellow pages. Thomas (white vamp) wants him to investigate a case for him. A movie producer is being cursed, and people around him keep on dying in strange ways. Harry jumps right in and there's plenty of action on every page. Demons, puppies, vampires, police, mysterious assassins, wizards, succubi, it's all there.
We get to see more of his growing relationship with Murphy, Ebenezer and Kincaid ome back in and there are a few twists that were definitely a surprise and an ending that seems to move Harry in a different direction to where he has always been left before. This time his life will have changed forever.
Its hard to say more without ruining it - suffice to say if you liked any of the other books you'll love this one. If you're new start with book 1 and work through. It's worth it.