I'd always thought this series was more of a young-adult paranormal type, more of the 'twilight' genre than of the 'true blood' genre. But it turns out there isn't a very clear distinction. The characterisation seems 'young-adult-ish' to me. Cassandra herself feels a lot like she's about 19, although I don't think we're given a clear age. A lot of the descriptions of the male characters leave a lot open to the imagination (although louis-cesar is a more distinct character, and I liked him a lot), but I generally get the impression that they're more goth teen idol, slim and pale, than they are housewife's wet dream, big and muscular. But then, there truly is graphic sex, not just the fond longing of teen vampire love. So it's hard to know where to place it.
Anyhow, it is actually well written. The storyline is complex, and you do have to pay attention to who is who, and what happens when. It's not something you can read just for the thrill of sex. Well you could, but you'd skip a lot of interesting pages.
I'm going to find the next one soon :)