I had always wanted to read Gantz, but all the reviews and stuff I would find said how mature themed it was. It would say something like, "If you like a lot of boobs and tons of unneeded bloody scenes than this is for you." That kind of thing turned me off from reading it, but eventually I gave in. One of the best decsions of my life.
Story: There are three arcs to Gantz. An introduction one, a middle one, and a finale. That is not very descriptive, but that is how it goes in my mind. One sets up the next very well. So basically you die and are sent to the Gantz room. The Gantz room sends you off to kill aliens with super powered suits and high tech guns. Seems simple enough, but if you read all of Gantz you will realize how in depth and well written Gantz is. There is also love and other themes too. In this manga people are gonna die and people are gonna barely survive. There is no point where I thought, "Oh shits hitting the fan right now, but somehow they will power up and survive." It was more like, "Oh my God, he is gonna die, and the manga is going to change forever." Also there are vampires, I know, really random. They are a third party who does not fully make sense yet, but I am sure they have some huge meaning yet to be determined.
Art: Gantz has some of the best art in all of the manga world. It is really detailed from the characters to the background. Everything looks amazing. The only knock I have on it is that in some action scenes it is so detailed that I cannot distinguish what is what, but do not get me wrong. This is some top notch art work from top to bottom.
Characters: The characters are amazing in Gantz. They are all unique and have their own views. The aliens are all so one of a kind and cool looking. They are just spectacular in every sense. The main character Kei starts off unlikeable, but eventually becomes very likeable... as well as a BAMF. Every character has such a distinguished background that every decision they make I think, "Oh, I could see why they do that." Some characters have sad stories that just makes me feel like I can connect to them somehow. The way some characters are potrayed in death is really well done, and it shows their true colors. Mistakes are often made by characters in this show and they pay the consequences. The "this is your only shot" type of thing that Gantz brings makes it that much more exciting.
Overall: Overall, I just love this manga. I read through the chapters so quickly. It was evident that I had become a complete addict after 30 chapters. Even when I did not like or I did not think I liked where the story was heading I was always coming back for more. This is a must read in my opinion.