These are readable without reading volume 1.  The gist is that there is a cyborg warrior treading thru apocalyptic cityscapes on his way to the mother of all gunfights.  His own side is gonna kill him when he’s finished and he knows it.  If you’re into deeper themes/motifs, there are a bunch of Zen/spiritual ones in there.  Enjoy!  Start reading here:  Echo Vol.2 Chapter 1