I recently read Fallen and Torment by Lauren Kate. When I learned that The Betrayal of Natalie Hargrove was her first novel, I thought I'd pick it up, too.
The Fallen books are quite different from Betrayal - which is a fairly straightforward rags-to-riches, riches-to-evil tale. Though I was surprised by the completely different feel of Betrayal, I enjoyed it just as much as I did the Fallen books :)

Natalie Hargrove grew up on the wrong side of the tracks with an alcoholic mother and an abusive father. In her early teens, though, all that changed. Daddy went to jail and momma began her profitable cycle of marrying for money. By the time Natalie is a senior at Palmetto High, she and her mother are firmly entrenched in the right part of town and it's society. Natalie is involved with Mike - the most desired, popular boy at school and momma is about to marry one of the wealthiest (if dorkiest) men in town. On top of that, Nat is poised to win Palmetto Princess, her towns over-blown version of Homecoming Queen.
Unfortunately, things begin to fall apart. Natalie's father gets out of jail and begins harassing her with text messages. She learns that Mike may not win Palmetto Prince - Justin, a boy Nat dislikes - is instead the front runner.
Then the opportunity presents itself to play a prank on Justin - making him look like a lecherous fool in front of the entire town and sending his Palmetto Princess votes Mikes way, instead.
The prank goes terribly wrong, of course, and Justin ends up dead. Here begins the descent into evil as Natalie and Mike try to cover up their part in Justins death and push the blame onto someone else.

I thought the main characters were well developed. Natalie and Mike both had unexpected depth. Though the majority of the secondary characters (Tracey, Double D, Slutsky, Kate, Baxter) were pretty one-dimensional and flat.
I thought Mike and Natalie's relationship was surprisingly sweet and authentic. It made the difference in the book for me, taking it from 2.5 stars to 3.5 stars, though it still didn't quite merrit rounding up. A fun, quick read.