Film screenplays evolved from directors notes to full-blown dramas.  They aren’t plays, because the scope is greater.  They aren’t novels,  because so much is conveyed visually.  But like both, the writer needs to establish dramatic tension, narrative flow, and character development.  Failure to do so can be fatal.  This years winner for best original screenplay, Her by Spike Jonze is not out on DVD yet, but you can enjoy the other nominees while you are waiting.