"The slowest, most filler-filled manga I've ever encountered. The focus was so much on aimless wandering, insane people and monster metaphors that what mattered got ignored. And it ended at a random point, with NOTHING explained or resolved." - from my tags.
Dragon Head's ending has to rank as the worst ending ever. After countless filler chapters, involving running from random nutjobs, wandering around ruined areas and, at the end, some fear cult bullshit, it just ended. After drawing the story out for 40+ chapters more than needed, not even the reason for Japan turning into hell was revealed? Wonderful. What a complete waste of my not-so-precious time.
I don't know why a new volcano appeared (the translation referred to it as Mt. Fuji..), and I don't care. I don't think the mangaka did, either - he/she couldn't have been more vague.
If the story had started before the disaster, introducing the characters and showing how they acted before everything went to hell, it would've been more involving from the start. If flashbacks had been used effectively, rather than there being an endless amount of filler chapters and pointless/totally needless discussions about fear with monster metaphors, it would've showed the 'before and after' of the character's lives; making the new hellish world disturbing to see. If Teru and Aoki had become romantically involved, it would've added more danger; making readers fear for their relationship.
(Basically, I should've re-read Battle Royale instead!)
...If, if, if. The characters never became anything other than cardboard cutouts because of the mangaka not handling them right. And when that's put together with a mostly aimless story that never goes anywhere, which ended in the worst way possible (without a proper ending), you're left with an empty shell that, in truth, isn't worth reading.
I regret reading all 89 chapters because of the hope it'd improve. It never did. I dropped my score from 6/10 to 5/10.