When I first came across the manga, Hellsing and Black Lagoon were my first thoughts about it too (Kohske's style immediately reminded me of Hirano's).
Bumping this primarily to say drop the show and read the manga :V I'm watching the anime because I'm heavily invested in the series, but while it's not a bad adaptation (except for the piss poor art, PLEASE be decent in the BD release) it's… Gangsta got me in from all the little nuances in the manga that allude to character personalities and flaws, as well as Kohske being REALLY good at dropping lil hints that do or may suggest something big later. They're not all very obvious, but I think that's what makes the writing good.
Unfortunately the anime is compressing A LOT of material into 12 episodes. I feel like they may try to end this season at the end of Vol 5, or WORSE the first half of 6... There's a pretty good yet emotionally horrible place to put a cliffhanger if they go into volume 6... so I'm hoping it ends with Vol 5... Anyway, a lot of the little nuances dropped into the story were cut out of the anime. It's to the point where it's getting way too dry for my liking. They're keeping important plot points, but Gangsta is awesome because some of the little stuff is SO touching and/or important. Especially when it comes to Alex and Worick/Nic's backstory. ESPECIALLY their backstory. That was the part in the manga that sold me on this series, and they compressed in a way that told the story but only partially expressed the full emotional gravity of that backstory. Like the anime's telling of the story... is adequate but it's missing a lot of the emotion that's in the manga and that makes it sad for me.
That and due to Kohske's bad health, the manga updates rather slowly. So if you're only watching the anime, it's gonna be a loooooong time before S2 is ever made. If it ever gets made. This is a good series in the fact that even though the wait between chapters can get bad (usually there's no more than 1-2 months between chapters, but very rarely is Gangsta in @Bunch two months in a row), it is rather worth the wait. Except chapter 41 ended on a horrible cliffhanger and chapter 42 finally comes out 2 months later AND NOW LETS GO SEE WHAT THESE OTHER CHARACTERS ARE DOING :getlost: rant
For me it was a breath of fresh air. I ended up reading the series on a whim due to seeing Nicolas' design, and I haven't been disappointed. Except in the anime hahaha. It's not complete trash, but it doesn't do the manga justice at all.