I saw Watchmen in theaters when it first came out, so I knew the story for the most part. This took out the mystery aspect of this story, and just left me to enjoy the writing and the artwork. I didn't love the movie, although I liked it well enough, I thought it was overlong. It does follow the graphic novel very closely, though, so I imagine that's why it was long. I liked the book better, in this case.
I would recommend this only if a person liked graphic novels, but otherwise probably not.