It's been a long time since I have read a few, but a lot stayed with me. I think hers is the only vampire universe I really enjoyed. The main reason I love Anne Rice's vampire universe is that it is about vampires and a 'realistic' take on that with a motive on human. I think this is also the reason why the books have an adult appeal. It always seemed to me that by creating certain kind of rules in her universe and never crossing them, she shot quite a few birds. And in the end this is what made these novels so good. She is not trying to keep anyone happy. She doesn't apologise. Some general spoilers ahead.
Vampires do not have actually relationships with humans. That was the first thing that won me over. Most importantly, romantic relationships. They are not attracted to humans in any way other than seeing them as food. Considering the nature of the fantasy species we call vampire, this provides a very solid sense of realism. I think, I've always found the idea ridiculous, not because vampires are far more superior than humans and immortal, but simply because humans are their basic food group. But then they are cut off from earthly pleasures, which makes it a perfect explanation for their extreme lust for blood.
There are very few vampires in the beginning of this universe, because being a vampire is not a dreamy way of life. It's really dark, suffocating and disgusting. Lots of brilliant points. That turning a human to a vampire is a very big deal. That most vampires do perish, because they cannot adapt to the times, or any change. But then there are almost nothing to adapt before modernism really took its roots and then she spins this on its head perfectly with the twentieth century; the new breed of vampires and the new 'zeitgeist'.
Blood is seen as knowledge and information by vampires. They can't drink the last drop. That they 'learn' from it anything unique about the human. Vampires actually have a disturbing appearance in light, up close. Even a small amount of sun light affects them. There was a detail mentioned -related to Lestat?- a vampire can harm his own sense of hearing by the sheer power of his voice.
These and a lot of more I can't remember now, all brilliant details she has built around a fantasy species, have made it delicious. All the between the lines details about defining vampires as the beings existing trapped at the edge of the nature, in suspension, exploiting its laws... can't move anywhere else. Because besides a few very certain rules, they don't know about themselves; being a vampire either. Nobody knows real limits or powers of vampires. Or what a human will be as a vampire.
And as a result, it seems these stories are telling what is all about being a human, more than a lot of other non fantasy fiction or nonficiton telling about humans. I realise that today these grand themes are worn out, oversimplified, even emptied. But I just checked, 'Interview with the Vampire' was published in 1976 -I thought early 80s for a moment- and for that period and a few decades after honestly, it is a very big deal to be able tackle a grand theme this way. It's philosophy, lol, it is ontology in disguise. Also a good proof that fiction is the best way to get around with philosphy.
Probably too long for a first post, but I haven't thought about Anne Rice for a long time and felt the need to write what I feel when saw the title. Looking around today, esp. the last examples of the vampire genre, this lady's work is still at the top. Politely put, a lot of key elements in recent works 'inspired' by her anyway.