[MMM]

Time Magazine has rated Watchmen as one of the top 100 pieces of fiction ever (not sure if that was limited to American fiction). I have read the book, and its reputation is well-deserved. It is a very intelligent look at superheroes as real people. People who are political, and have serious psychological issues.
It is also a look at the world through Cold War eyes, which may be hard for younger readers to grasp.

In the Watchmen, a group of superheroes basically wins the Vietnam War for America, allowing Pres. Nixon's popularity to go so high he is elected for five terms. He thanks them by making masked heroes illegal, leading to a breakdown far beyond anything in The Incredibles.

I liked the movie a lot. It is very violent, but also very talky (and long) so if you are looking for The X-men, Watchmen is probably not a good pick. However if you like adult themes and thinky movies, you will probably enjoy it.