Evil is not the mugger on the street or even your average rapist or murderer. Evil is the system that fosters them. Evil is created often legally, and there is nothing conventional crime fighting can do to stop it. 
 So i trashed the Watchmen movie and didn't think i'd ever read the book. But i did, and i am glad. Won't say anything that has already been said. So will stick to a free flow of thoughts. 
 This is a truly complex piece of art right here. Moore's worldview to me seems somewhat misanthropic, most of his characters are social outcasts by choice. They treat the rest of the human race with derision and pity. 
 The book is heavy with ironic political analogy. The 'American adventurism' described is both a twisted play at actual Russian invasions into that region as well as strangely prescient of modern day American ventures into the area. 
 Some concepts like the overarching fear of nuclear war are somewhat dated, but gaining increasing significance as we proceed into an increasingly trigger happy 21st century. 
 Moore has no pity for American war mongering and meddling in other countries' fates, and is directly critical of the political establishment. Nixon is particularly derided. And even hinted at as being shadily connected to the JFK assassination. 
 The storytelling is a multi layered affair. I feel he has used the comic book format to maximum effect. The pictures and words carry their own thought streams and are almost independent of each other. Yet they mix and mesh together to form a compelling and thought provoking story. 
 The artwork, while nothing too spectacular, is detailed and provides a lot of information in a did-you-notice-that-graffiti-on-the-wall kinda way. No detail is added idly. Every thing seems to have a purpose, efficient use of space I would say. 
 The story dissects good and evil and attempts to find an underlying basis. And fails. It ultimately tells you that the human race is doomed to recreate cycles injustice and evil, to destroy itself over and over again. 
 Admittedly this type of worldview and message plays a lot on your spiritual beliefs. There is a lot of philosophy and metaphysics thrown on the table. To me as Muslim it was an insight into a different perspective on life.