Holy smokes this manga is crazy. First of all the artwork is spectacular, let me just get that out of the way. Ito really excels at drawing creepy figures and imagery. There is also some incredible body horror the likes of which I may never have seen matched in any medium. His use of shadow and light is masterful in setting ambiance.
If the art in this book isn't matched by its writing, then it's surpassed by it. This may have been intentional for a book whose defining them is the spiral shape but this story really spirals out of control. Every single chapter had me shouting "Wow! This is the climax already because there's no possible way things can escalate from here." To my delight I was proven wrong every time as the story just continues to build and escalate until nearly the very end.
The world that is built in this manga is just so fascinating and imaginative. It's jam packed full of incredible sci-fi and horror concepts that are all executed really well and will surely stick with me for a long time. It's one of those books that I wish I could read again for the first time but will certainly come back to again even though I know what's going to happen.