This film begins with the words- "This is not a love story". And indeed it wasn't. Although there was a hint of serious undertones in the light humor throughout the film, the levels of this sober mood never peaked high enough for it to become; a love story.
This was actually what made the movie so good. It wasnt a typical romance; it was real. Yes- there may have been a few singalongs and animation edits along the way but aside from that; the personalitites, actions and feelings of the chatecters were real- you could relate to them. And isnt that want everyone wants in a good film?
There are also echoes of similarity to another film that Zooey Deschanel stars in- Hitch Hikers Guide to the Galaxy. Both subtly mock the actions of the human race and question whether we act on what we feel or what were told to feel. However this is done subtly using clever satire which gets through to us by the appearance of the friendly voice over who speaks at intervals in the film to offer helpful background knowledge and general tips on life.