Gantz is an original idea. Making it gruesome and having extreme situations takes it to a whole 'nother level. When I first started reading it I was like, "why did that person have to die? they were pretty cool" it made me kind of upset, but that kind of of thing makes Gantz a "what's next?" and not predictable storyline.
Besides Kurono, to see what happened to the other characters before becoming Gantzers can be pretty intense and shocking to people who ignore how bad the world can be. The author isn't afraid to make people stir.
Raising my fighting spirit.