I read Watchmen for the third time, a couple of weeks ago. I think it may be the first novel I've ever read thrice. First time was in the late 80's; must have been shortly after it came out. Someone loaned me "The Dark Knight Returns" and "Watchmen". Blown away, by both, but I haven't re-read DKR. Maybe I should. Re-read Watchmen just before the movie came out. The movie is worth seeing, but only after you've read it, if possible.
It was a joy to read, each time. Just a wonderful piece of work.
Theodore Sturgeon said something like "good science fiction is good fiction". A good graphic novel is a good novel.
DKR is excellent in comparison to superhero comics that came before; Watchmen is just excellent. DKR is kind of "Batman as Clint Eastwood" and it works on that level. Watchmen is kind of "Superheroes as extensions of the Id" and it works on many levels.