Watchmen is a 1987 graphic novel created by writer Alan Moore and illustrator Dave Gibbons that has since become universally recognized as one of the best of the comic book medium. Magazines such as Time have gone so far as to rate Watchmen one of the 100 best novels of the past quarter century.
The story takes place in an alternate reality during the mid-eighties. Nixon is still president, and superheroes (who mostly don't have superpowers anyway) have been outlawed by the government. This however doesn't stop a group of heroes from donning the tights again when one of their own is assassinated. The heroes include a guy with an ink-blot mask named Rorschach, resident sexpot Silk Spectre II, and the one guy with actual superpowers, a gigantic blue guy called Dr. Manhattan who exiles himself to Mars.