Should I read or should I watch

I am trying to decide whether to read the History of Violence graphic novel and (assuming I like it) watch the movie or just watch the movie. I've heard tell that the movie is quite good, but my general rule is source material first. I am not sure if I feel the same way about graphic novels. Graphic novel length is often short enough to fully capture on screen. From Hell was a giant and was pared back for the movie. I doubt that the Watchmen could be completely told either. I think History of Violence is short enough.

If it is short enough, should I still skip the comic and go straight to the movie? So hard to know.