This story had potential but it was lost along the way.
First off, this plot reminded me of the romcom with Sandra Bullock with a similair plot. So Jennifer wakes up and finds herself to be married to very attractive psychopath. Obviously things get out of control fast enough.
Mike Vogel was (as always) a delight to watch, he portrayed the crazy obsessed Russell quite well. Brenda Song, not so much, sorry. Her expressions are too comical. She would have been a great fit if this was indeed a romcom. Her performance made this movie feel like I was watching a parody of the movie and my God whoever thought of that end scene... that ruined the entire plot in itself. [spoiler] so you have just gone through hell, parents murdered by this crazy obsessed guy, doting husband murdered by the same guy and you receive a letter of your dead husband, read it and drive off into the 'sunset' half smiling, all's well that ends well. That is ridiculous. I'd imagine you'd be reading that letter bawling your eyes out. [/spoiler]

So, potential wasted.