If you're going to try this series out, please keep in mind that it's basically an excuse for a bunch of voice actors to have fun and sell C Ds
. The original series' animation is generally awful, and the sequel's is on-model, but uninspired. There's a particular scene near the end of Gluehen
where Youji is screaming and sobbing and yelling like a madman about how he doesn't want to hurt anymore and the animation is just a slow pan across his eyes. Shinichiro Miki acts the hell out of this scene, and to see how the animators wasted the opportunity is disheartening.
That said, it's the voice acting that makes this show. What these characters lack in cohesive narratives and decent animation, they make up for in charm. Just watching them wander around reacting to events and each other is can be entertaining. What backstories they do have (Aya's is quite detailed) add some interesting color to their reactions and situations, and if you start overthinking it some, it might actually make sense!
You can kind of tell the series was developed by an actor: you can almost hear Takehito Koyasu thinking, "What will let us really *perform* for the audience?" So try not to pay attention to the fact that the situation is contrived and easily prevented or that Aya only knew that guy for two days at most or that we already did a "bad guy butchers innocent young women" plot. Pay attention to the fact that Omi is having a PTSD flashback in the middle of the mission room and he's obviously distressed. Listen to that *scream*!
Or hey, pay attention to the fact that Omi's having a screaming PTSD flashback in the middle of the mission room, and the other three have no idea what the hell's going on, or where Manx hid the extra straitjacket. Sometimes, you gotta sit back and laugh at the absurdity of it all.
Another thing that draws the fans is Schwarz. One of the highest (and least sarcastic) praises this series gets is that it boasts a set of four villains that are a) utter sociopaths, b) very happy with that fact, and c) 100% undefeated.
All in all, be prepared not to take things too seriously, and don't think too hard. Focus on the characters, not the plot. There's fun to be had here, even if it is contrived, angsty, and won't make sense without the CD dramas.