Watchmen

This is one of the first graphic novels that aspired to be more than just a comic book. OK, it still looks a lot like a comic book -- it has characters with names like Dr. Manhattan, and Nite Owl -- but it also touches on themes much deeper than the dangers of Kryptonite. It delves into the mindset of those who find it acceptable to don tights and stalk the streets in search of wrongdoers.
The book is interesting in that it doesn't necessarily hold these people up as heroes. They dress strangely, sure, but then it was written in the '80s, after all . In many ways the heroes are the weakest characters in the book.
It's smart stuff by some of the best known names in the genre/format. The writer, Alan Moore, was behind the graphic novel "From Hell," which was later made into a mediocre movie. He also wrote "V for Vendetta," which is due to be released as a movie later this year.