I'm in awe of Naoki Urasawa's storytelling abilities. He has a marvellous way of handling suspense by controlling the way critical details are revealed, or not. I love his crisp art style.
I think the work as a whole could have been much shorter, with many of the subplots pared away, and overall the series had the feeling of starting out with a brilliant premise but no clear idea of where it was headed. It would have benefited from tighter control.
All this says, this is one of the best manga I have read. Bravo!
I just finished Pluto again after about 10 years. It is also great. Reading Billy Bat now and that reminds me a little of 20th Century Boys.