I don't know if you meant to imply it was, but Twilight isn't in third person present but first past.
I'm seventy pages from the end of Eclipse, Volume 3 of the series - I read Twilight and New Moon earlier this year (review copies). While they're certainly readable in a clear though bland style, they're far too long and Twilight especially bogs down for a couple of hundred pages in the middle while Bella and Edward incessantly discuss their love for each other.
Considering that the central characters are modern-day 17-18 year olds, I found the novels annoying in their coyness about sex. Yes, I can accept that a young couple may decide not to sleep together, but not to mention the subject at all seems evasive to me and possibly writing down to Meyer's perception of a YA audience. To be fair, the subject does come up in Eclipse, but it's only taken two quite hefty novels to get that far...
I'm late to the discussion here, but this post struck me (last paragraph about sex and Bella/Edward). I teach eighth grade, and I read Twilight and New Moon last summer and then did a book-talk about them to my students. They were an instant hit, and the books circulated the classes all year long, engaging even some really reluctant readers--kids who certainly wouldn't have ever picked up anything longer or more interesting than the freaking goosebumps crap before. I can't speak to older readers (other than me, much older in my case!), but to the 8th grade girls, the level of sexual tension in these books was great because it was exciting without graphic.
I think something important about the sexual element (down to kisses being closed mouth) is that there's such an element of self-control for both Bella and Edward. There is this hunger (thirst?) that is so powerful, and so dangerous, when they have physical contact. Both young adults are fighting against their desire getting out of control and pushing them off the edge of something scary and thrilling. I think this appeals to the readers (in this case, my 8th graders, but obviously others as well) because it feels like their own experience with sexual desire. Make sense at all?
Sorry for all the parentheses (I'm addicted). Personally, I agree that the books had a lot of filler, and I have a real problem with how controlling Edward is, and how easy Bella is to control. I like Bella better when she is interacting with Jacob.