I agree with
Navarre: SM has fairly basic diction. She isn't too flowery in her prose. And that's definitely a good thing. Imagine this storyline coupled with nothing but the overuse of adverbs and compound sentences.
I feel like this is the way she talks (although I could be wrong; I don't think I've ever actually heard her speak before). Some writers write like they talk. And even if this isn't how
she talks then it's how someone talks. It's very indicative of a dialog-like style. It's nice it goes well with the narrative.
She also does a great job with her descriptions. I know they're long - and others have knocked her for it - but I can really see the things as they happen in the Saga. There are other books that I love where that simply isn't the case. Some are good story tellers, but that's where it ends. SM can write a book that draws on all the sensory receptors. I can smell Edward (like ice and Bath and Body Works Aromatherapy Eucalyptus Spearmint - for real - try it sometime

). I can feel that tingling and pulsating of Bella's nerves as she's hunted down over and over again. I can here her truck, their voices (and Edward is still talking in a British accent, I don't know why. This was even before Rob was cast so... Yo no se

).
I can see Charlie's house (I could draw a layout), I can see the Cullen property, La Push, Forks High, the Markses yard wear she first sees her and Jake's bike, Volterra

-- I can see all of it. And maybe it's not what SM sees (more than likely it isn't) but being able to convey these concepts to a reader is, in my opinion, the mark of a good writer.