The story revolves around a changing group of people (other than the main characters) who die but find themselves reassembled in an apartment they can't escape with a large black sphere (Gantz) that provides them with weapons, a power suit, and instructions to kill an alien target within a time limit. Those who survive are free to return to their lives until they are summoned again, with increasingly poor odds of survival each time.
The animation is reminiscent of the R-rated anime more common back in the '80s, with uncensored graphic violence, nudity, sex, and generally mature themes, and it's refreshing to watch an adult-oriented story that hasn't been watered down to receive PG rating (though it does have a jarringly out-of-place JPop theme song). The series covers about half of the story from the manga before concluding with an open-to-interpretation ending that, but that's better than ending on a cliffhanger that never gets resolved.
Gonzo Studios has a tendency to use unnecessary flashbacks or simply cut animation quality when they run out of time and/or money, and I can live with that, but they made a lot of choices which may or may not have been in the manga that simply that make no sense. Why is the population of 2004 Tokyo 95% Caucasian and why would they all look forward to seeing someone get run over by train and refuse to help? How can high school bullies, who look like they're in their 30s, get away with pulling teeth out of their victims? Why would a group of people, including a guy who easily beats up the biggest of the aforementioned bullies, stand around and do nothing when a guy carries a teenage girl away into the next room to rape her? Why do people who just died and see other people being reassembled in front of their eyes act like nothing strange is going on and refuse to listen to the main characters who are trying to save their lives?
The thing that will really have you shouting at the screen is all the times (and this happens a lot) when the characters stand around talking about how they should shoot the monster despite the time limit and immediate threat to their lives, yet no-one actually starts shooting. Two or three people will die before even one of them starts shooting while the rest still just stand there. Then, when half of them do finally join in (the rest still standing there watching), they charge towards the monster, guns in hand but still not shooting, until a couple more people are killed.
Overall, I do recommend Gantz, but it's frustrating to watch something that could have been so much better brought down by things that should never have been allowed into the series in the first place.
