At this point as a society, we've coupled zombies and comedy. I'm sure there are a myriad of compelling psychological reasons why this is so. But whatever our complex need to attach comedic value to something as existentially horrifying as reanimated corpses, it manifests itself in an equally complex milieu. The zombie/comedy dyad operates within a very wide spectrum. Zombie movies can be hilariously funny, a la Sean of the Dead, or stark and terrifying, as in the original Night of the Living Dead (which uses only a sprinkling of comedy to balance the effect).
I think the other reviewers may have expected this movie to be a lot more screwball than it was. The fact that it wasn't doesn't constitute a failure. The slapstick zombie movie is only one type of a surprisingly complex subgenre of cinema. And this ain't it.
American Zombie asks viewers to suspend disbelief to its very limits, and assume that zombies are both real and that they are deserving of deeper consideration. For anyone who ever spent more than an hour in discussion of zombie physiology, cause, and social consequence, this movie is like candy.
The movie (which is conducted like a documentary) follows four "high-functioning" zombies living (also dating, consuming, and working) among regular humans in Los Angeles. Each subject has his or her own take on his unique "condition."
The general feeling of the film is the same as that of a documentary following people diagnosed with an untreatable medical condition. Ivan begins with the statement (paraphrased), "I don't know how long it will be before my body decomposes, so I'm living each day at a time." A second character, Lisa, is first seen wandering (a little plaintively) in a cemetery, admiring funerary bouquets and wondering if she'll ever know who she was in life.
The film plunges into the cause of zombiism: namely that some people carry an inert virus in the brain that isn't activated until the host is the victim of violent death. American Zombie then quickly investigates other compelling ideas like the implication of being an adult with essentially no identity and how the families respond to a loved one who was first a victim then a reanimated corpse with no memory of their past.
The film also investigates how the civil infrastructure manages a zombie population existing in tandem with the human population, from city government census agencies to a not-for-profit advocacy group working to avoid sweatshop-type exploitation of zombie workers.
There are a number of secondary themes, from zombie sexuality to zombie art. The effect is of a fully fleshed out scenario that lacks the gaping continuity holes that characterize 95% of zombie films. It gives the considerate viewer ample material to chew over and provides plenty of meat for discussion (pardon the necrophagy pun). Which, for an audience who groans at every inconsistency and implausibility that plague the genre, proffers a film that addresses our core hunger for a socially responsible zombie movie.
Finally, the film also follows the "filmmakers'" creative and production process. This is actually a little annoying for the first half of the film, and feels a little Lisa Ling (National Geographic)-ish. However, when the filmmakers disprove their own thesis statement, and find that their subjects are not the same as a cancer patient and cannot simply assimilate into the human population, the coverage of the filmmakers takes on a much more urgent life.
The climax of the film is a complete shock, which alone is rare in a well canvassed subgenre of cinema such as zombie movies. I won't ruin it. So I will conclude by saying American Zombie is as much unlike a George Romero or Sean of the Dead movie as one can get and has what it takes to delight and surprise veteran zombie aficionados. More casual audiences might lament it's lack of visual one-liners and lack of back to back gore scenes. But fans of the genre should seek this one out, as it's an infrequent example of a film doing something different with the zombie theme. It's a welcome addition to the canon.