I guess. I don't know what it was specifally, I've just started to find myself losing interest since I finished Club Dead (book 3). I don't know, maybe after Dead to the World (book 4) I might find my interest renewed. With the Dresden books on the other hand, I'm anxiously trying to work through my ever growing to read pile, so I don't feel guilty getting Death Masks (TDF 5). I'm also read the first book in Kim Harrison's The Hollows series, and I also enjoyed that more than the Sookie Stackhouse books.
As for the True Blood show, it's probably one of the only situations I've come across where I actually enjoyed the show alot more than the source material. True Blood is way better than the books IMO.