K, there is sooooo much debate about Stephenie Meyer's books going on that I, because I have nothing better to do, am going 2 put my 2 cents in. Many people, from many different backgrounds, have many different opinions on this series. Some say it is immoral, some say it isn't. I don't think this needs to be such a hot-button issue.
How you see these books depends on your viewpoint in general. Not everyone is going to think of these books in the same way. Personally, I think that they are well-written and not even close to entirely inappropriate. The fact of the matter is, most books for young adults today read like smutty romance novels that you can pick up in grocery stores. By comparison, Twilight and its sequals are extremely tame. If they are as bad as some people seem to think, then why are they sold in LDS bookstores? I'm not saying that young, immature people should read these novels; I have a cousin who is that I wish had waited a year or two. However, I do reccomend these books to my older friends, because I think they are very very good.
First off, Edward and his family are not demons. If they were, they would not behave in the way they do; refusing to prey on humans, encouraging Bella to keep her mortality. The fact that Edward thinks he is a demon and wishes he was good, but thinks thats a hopeless wish kinda proves my point.
Second, there are several Mormon principles that can be found, even though none of the characters are Mormon. They don't drink, they dont smoke, they dont do drugs, and they dont have sex until they are married. When the last one did happen, it was described in a beautiful, non-graphic way, giving the event the beauty and respect God intended.
Finally, the love between Bella and Edward is a wonderful example of the way love is supposed to be. It is unconditional, unselfish, and not shallow, but is more on the level of the soul. Sure it can be viewed as bad that Bella wants to become a vampire to be with Edward, but I choose to appreciate the fact that she shows a kind of love that is rarely seen today in "popular" culture.
All in all, the main thing is a person's individual feelings and views. Like anything else, your opinion of this book is in your perspective. I, for my part, love these books, and am grateful that Stephenie Meyer chose to write them