Most of the direction of things is pretty easy to figure out if you've got any experience with World of Darkness. I don't know if Charlaine Harris is a fan of White Wolf, I wouldn't accuse her of plagiarism by any means by there are a lot of parallel ideas/ themes.
My girlfriend is a total junkie for the books, she can't keep herself from throwing me out spoilers about them if she thinks they've changed the show enough they aren't going to go that route, so I do have some notion about where Eric is headed or supposed to be headed. he's all right but he sort of euro-trash douchebaggish for me. So far Bill is the only vampire I really like, ever since Sam threw it out that there are werewolves I keep praying a pack will roll into town and do what werewolves do best, wreak total havoc on vampires. That is absolutely my World of Darkness past experiences speaking, I was always more into ultra-violent werewolves than snobby vampires. If Harris' werecritters are anything like WoD the only one with a chance of surviving probably would be Eric, so that might make you fans happy.
Okay I'm going to stop throwing out my WoD prejudices and stuff and say that I really enjoy the hell out of this show. I hope they give the guy who plays Jason an award at some point, the guy is brilliant at playing a moron. the whole cast is great, Tara is probably my favourite character which is interesting since I hear she's barely in the books. I'm all for changing the story of books in an adaptation if it makes the story better, and sometimes it really does. I would therefore advise any of the book fans that are bummed out to be patient, and that's what Allan Bell (Ball?) has been saying too.