If you liked A Beautiful Mind, you should like this. It's basically a play adapted for the screen and doesn't really need more than 4 actors (1. intellectually towering dad that went mad, 2. normal and successful sister with high displacement instincts, 3. not so normal and not so successful sister, yet daddy's girl, wondering whether she needs to go to the funny farm too, and 4. her male math student love interest, all of them casted great in the film version).
Frau Paltrow played it on stage in London for a while before committing to the movie version, maybe that is why her performance is so good.