This review nails it on the head.
http://talkbacker.com/movies/reviews/new/skin-review-unorthodox-film-far-year/id=30596
The director, Jonathan Glazer, said that he wanted to take a minimalist approach to the material, stripping the plot to the bare essentials. Unless you've read the book (which I haven't) and know the ins and outs of the plot, my fear is that he went too far. It is impossible to follow all that's happening without knowing the plot beforehand.
I encourage everyone who wants to see this film to read a few reviews beforehand and go to Wikipedia and read what's the book is about. Under the Skin is rare in that in order for it to be watchable, you have to know what's going on.
I give Under the Skin a 'D'. The director/writers tried too hard to be edgy, experimental, and abstract but forgot to make a filmgoing experience worth our while.