The movie is, like Sin City, based on his graphic novel.
The graphic novel was great. Occasionally the art was a little underimpressive, but the writing was phenomenal.
However, the release date means the movie is a dud (at least, according to Hollywood), since it's not out around the peak seasons for what the wheels consider major moneymaker pics.
I don't know if dud is quite the right word. Clearly they aren't expecting it to be a blockbuster, which given that it's a movie about a battle that 99% of the populace never heard of is a smart expectation. But they aren't releasing it in January, which is when they put out movies they were seriously thinking of releasing direct to video (and often should have).
And like Sin City, it looks like it may be all visual style, and no depth.