The science-fiction underpinnings of Never Let Me Go are only hinted at in most of the advertising for the film, which is probably a good idea, because it's first and foremost a love story. Granted, the story takes place in an alternate reality, where the characters are all pawns in a grand experiment in selective health care, but don't go into it expecting lasers and laboratories. The movie is based on a book by Kazuo Ishiguro, the author of The Remains of the Day, which was about an emotionally repressed butler, so that should give you an idea of what to expect here.
Vampires, monsters and clones are invading your DVD collection. Let them in! You won't regret it!