I read the first one on a friend's recommendation. I found the prose to be overblown and very melodramatic, the characters to be shallow cut outs who I couldn't find any hint of likable emotion to relate to, and the entire story struck me as being extraordinarily creepy. If a guy stalks a girl, sneaks into her bedroom, acts all pissy and prima donna whenever she's around, and yet is still declaring himself to have 'true love' for her, that's grounds to have him arrested. What you don't do is form a relationship with him.
From what I've heard from this same friend about the rest of the series, it only gets worse, Stephanie Meyer decided she didn't need an editor, and apparently belives that the first thing she writes is the best (which has never been true in the entire history of literature), so doesn't need checking for inconsistencies. There are some major biology related plot holes in how his apparently crystal like skin can move, how his sperm remains body temperature and thus able to impregnate her despite his being at room temperature, how apparently in one hundred and eight years he has constantly been a teenager yet somehow never had a sexual thought about another girl.
And as for the overall moral, despite the aforementioned mind-numbing stupidity of the girl essentially falling in love with her stalker in book one, there is a very unhealthy message that comes through with her wanting to be a vampire in order to (paraphrasing from the book here) stay 17 forever so she doesn't suffer the horrors of growing old. Only a teenager would think that, and only a teenager would be so clueless as to think that was actually a good thing. She at least wouldn't be lonely because starting in the first book and apparently continued throughout she shuns her friends and close relations in order to continue to foster her romance with her emotionally dead, cardboard cutout stalker of a boyfriend and his murderous family.
If you think Twilight is a good love story with a positive message, you are provably wrong. If you wish to tell me I am wrong, fine, but I would at the very least like some clarification as to how Stalking Equals Love to a 17 year old girl.