Meyer had a good idea, it came to her in a dream apparently, and she wasn't afraid to go with it. She, as much as I hate the phrase, thought outside the box, taking the well known lore about vampires and altering it, making it her own. I find this a gutsy move, admirable, and I'm jealous I didn't think of it. So her vampires sparkle in the sunlight, so what? That's the nice thing about mythical creatures, they're mythical, they can be anything you want. She made them more real, emotional creatures instead of just monsters. Coppola did this a bit in "Dracula" too, making the immortal Count somewhat sympathetic (casting Gary Oldman helped.) I also like how, in the last book, she starts to explore the scientific possibilities behind werewolves and vampires, like maybe they're not strictly supernatural, but preternatural.
I started with the movies, more accessible I guess, I read the books because I wanted more. I like everyone's back stories, stuff that's not included in the movies because of time constraints. And I enjoyed seeing how the screenwriter, Melissa Rosenberg, chose to adapt the books, since a lot of the action takes place in character's heads. If I had been a dedicated fan of the books before I saw the movies, I probably would have been greatly disappointed. They're not great films, just like they're not great books, but I gave up long ago up hoping the movie will be better, or even as good as, the book, because it's just not possible. Unless you have a really lousy imagination.
I find myself wishing Meyer would've done something like making the series open-ended, allowing other writers to continue with new books. It's not like her writing style is hard to copy. There's certainly enough material and storylines to work with, and she probably would've made another boatload of cash. But that's just the fangirl in me, not wanting the fantasy to end.