If you like the game, this is as close as you're gonna get seeing anything that is close to what happens in it. If you haven't played the game, don't like messed up BL, or enjoyed the anime as the only piece of Dramatical Murder content you've consumed - this isn't for you.
Story: It's the bad ends for each love interest. If you've played the game, you'll know what those entail. If you haven't and have only watched the anime, uhhh, get ready for a surprise. It's not an overall plot, but rather mini-episodes of what would have happened if Aoba made the wrong choice towards the end of the game/anime.
Characters: All the main love interests from the game. Doesn't really tell you anything about what they're actually like, and only shows their "dark side", without going too much into the lore of the game.
Style: Dark, gritty, dirty. It does a good job of depicting the bad ends without showing too much. It shows juuuuust enough for you to get the vibe.
Recommendation: If you played the game, watched the anime and wanted more, this is for you. I liked it. It was authentic. I'd recommend it. Though if you're more of a Given/Sasaki to Miyano/Umibe no Étranger person, this is very obviously not for you. Rated slightly higher for authenticity.