Since the year 2000, Marvel Comics has been reinventing their characters, trying to have more mature, innovative plots and artwork. (Actually, Marvel Comics has been reinventing their characters since they came into business, but the past few years have been one of the more dynamic periods).
In 2003, Garth Ennis, the creater of the famous Preacher series for DC Vertigo, wrote a five issue miniseries featuring Thor in a battle against a crew of zombie vikings. Ennis and his artist, Glenn Fabry, made the series rather graphic, earning the book an MA (mature audiences) label.
The series starts with a crew of Vikings raiding a village, and showing their acts of rape and slaughter. They plan to sail to America, where they will be free to rape and slaughter all they want, but are struck down by a curse from the village's wiseman. Instead, they sail for a thousand years, becoming zombies, and then attacking New York City, invincibly slaughtering everyone in the city. Their magical powers even enable the chief of the vikings to give Thor a beatdown.
While the vikings continue to murder their way through Manhattan, Thor and Doctor Strange go to look in the timestream for some warriors who can stand against the vikings. They find a Viking woman who wants to be a warrior, a crusader killing heretics, and a Nazi fighter pilot who all are magically transformed into a force that can fight against the Vikings. With this group in place, the five of them go back to Manhattan and defeat the Vikings in short order.
The plot being described, I will say a little bit about my take on this comic. Personally, I didn't find anything interesting, challenging, or different about the story or characterization. Thor is not the easiest character to write, usually depending on his imaginative cosmic settings rather then on any interest that would come out of his rather straightforward, upright character.
Garth Ennis could have tried to reinvent Thor, by pointing out that the warrior ethos of Norse society has little to do with Marvel's traditional portrayal of the chivalric Thor. He could have explored the moral issues of Thor's rather unlikely companions. He could have tried to portray Manhattan under the siege of the undead better. Instead, one of comics supposedly innovative talents gave us another story where an army attacks Manhattan and is repulsed after a short battle, leading the denizens of the Marvel universe to wait for next month's apocalyptic battle. The basic plotline is not that different from the late 80's Inferno storyline.
As for the art, it is approriately realistic and gory, and manages to display the sadism and brutality of the story quite well. Much like the story and the characteriation, nothing in the art is innovative or noteworthy.
I have not read Ennis' famous Preacher series, but I hope that comics fans have not been making this much noise about it if it is as bad as this.