I read the Watchmen book (winner of the 1988 Hugo Award in that year's special category) when it came out, back in the Late Pleistocene when I was in college. I am not ashamed to admit it was the first graphic novel I ever read, though I had read series comics as a kid (Weird Tales, Swamp Thing, random others), which I never liked as much as, say, science books. I got more satisfaction from learning about the life-cycle of a T-Rex or an O-type star than seeing Superman defeat yet another straw man. Then I discovered SF magazines in middle school and became was hooked on the power of the printed word over the rather weak material from comics. I even preferred them to most nonfiction. I mean, each month Isaac Asimov, himself, wrote me an editorial at the front of his magazine! Ben Bova and then Stan Schmidt wrote one, too, in Analog. As did Charles Ryan for Aboriginal Science Fiction and Ed Ferman for Fantasy & Science Fiction. So I was a literary snob, even as a kid.
Until a girlfriend handed me Watchmen. The art didn't get in my way; in fact, I rather enjoyed the added color and graphic interest. What blew me away was the writing and how Alan Moore and Dave Gibbons unified the written word and imagery into what felt to me a new form: This was a meta-work, something that would have been lessened if it were simply text - a first, as far as I can tell. This book was full of impossible yet completely real and sympathetic characters who were living out the themes of SF (and the noir mystery, among others) in one of the best stories yet written in the genre. And it was meta-meta-fiction, in that it not only represented important SFnal issues but also those of the comic genre. This is why I was so blown away by the book: I would have probably loved it almost as much if it had been just a short novel without graphics, but because the author and artist twisted iconic superhero-comic themes and asked hard questions of all its parent genres, this work rose above all others that came before. This does not lessen poor old slimy Swamp Thing, nor Batman, nor Superman, nor any of the other superheroes - nor the Golden-Age SF which provided the themes: Watchmen could not have existed without them.
It is thus an evolution and revolution all at once. And it was brilliant.
And the movie is, thankfully, brilliant. It adds another layer of meta (film), plus enriches the story with modern imagery and fine acting. The actors breathe new life into those barely human characters. I think my eyes were teary for 90% of the film.
In case you haven't seen it yet, I'm not sure if I recommend you read it first or watch the film first. But do at least one of those, and see the movie while it's on the big screen.