It's a Garth Ennis Batman story under DC's Black Label imprint for mature readers. It's okay.
The problem isn't Ennis's dislike of superheroes. I don't mind that. I just don't think he really achieves anything in this Batman story. It's not full-blown Ennis, despite still holding Batman slightly at arm's length and making jokes (via Alfred) about him being a rich man with too much time on his hands.
It also has eccentric fully painted art by Liam Sharp. (I remember him from Marvel UK's Death's Head. He's come a long way.) This looks spectacular and has bold, extreme caricatures, but it's not always easy to follow the visual storytelling. Ennis originally wrote this for Steve Dillon, whose style is so different from Sharp's that I simply can't imagine what it would have been like.
The story definitely has points of interest, though. Something's tearing apart Batman's rogue's gallery and killing off lots of famous names, but Ennis spends more time with the henchmen. You know, the faceless nobodies who go around with the Joker (WHY???) and obey his orders (WHY???). They only exist to be cannon fodder, but here Batman recruits one of them and spends a fair while learning about their point of view.
Killing all those big-name baddies works quite well. It's a common Elseworlds trick, but still effective. After that, Ennis has been having weird, extreme thoughts about Killer Croc, which are theoretically quite funny.
I don't dislike this book. It reads perfectly well and it's nice not to have the Bat-family. I don't regret buying it, but I also think it could have worked better than it does. The Killer Croc wackiness in the second half should have been funnier, which I suspect might be due to Sharp. He's gone so far into caricature that I think we lose the fundamental level of relatable people reacting to a situation, at which Steve Dillon was always brilliant. The art could have been more Ennissed-up. The script contains his trademark gore and bad taste, but this hasn't quite reached the visuals. Was this self-censorship, or DC policy? Dunno. It weakens the book, though.
In summary: interesting but mismatched. I don't think Ennis's script was a good fit for the experimental artwork, but there's plenty to enjoy in both.