It's a decent villainess movie with an interesting premise. The movie grips your attention until two-thirds in and that's where it starts to decline a little, mostly due to believability. Just as any acceptable evil main lead movie, there is karma to be paid, so rest assure that the moral of the story is still borderline morally agreeable.
Rosamund Pike carries the show as the lead with her stellar acting. She truly sells confident evil. The film would be anything less without her.
Overall, if you don't take the film too seriously it's a fun movie to watch.