Nier Automata's lore includes the contents of:
-a play called YorHa that had its first showing in 2014. This play covers A2's backstory and the event that caused her to defect from YorHa.
-a series of 5 concerts that featured a unique script for each one, voiced by the original VAs. Covers topics like the origin and creator of YorHa, A2's previous run ins with 2B and 9S before facing off in the Forest Kingdom, how 2B and 9S's relationship developed, etc.
The English VAs have only taken on the Concert Scripts. No word on there being an English production or reading of YorHa or anything, but Kyle and Kira did mention that they are willing to also read the novellas.
Sorry, if it's confusing.
Sooooooo,
translations of some snippits and summaries of the strategy guide have been released by Merutan. A boatload of thanks for their hard work. Some theories/impressions:
2B's Side:
-2B is pragmatic, so she pretty much just summarizes stuff. Merutan even calls her narration straight up bland. I'm a little sad we don't get to see into her mind more, but I guess that's what the Memory Cage was for.
-But there are small asides that show just how much 9S means to her.
Just him reacting to not having to call her Ma'am made her extremely happy. Seeing 9S injured by Adam made her livid, thinking she'll never forgive Adam for hurting him. (weh)
-2B not only suppresses her emotions because of her sense of duty, but also because
she feels YorHa androids are inferior to humans even though they look like them, and thus don't deserve to express the same depth of feeling. That's...so sad.
9S's Side:
-On the other side, 9S is always pondering. Deep down, 9S knows he has good reasons to believe that Machine Lifeforms have emotions and a sense of self like humans and androids do, but recognizing that means accepting that what he and 2B are doing is wrong. So he's simultaneously grasping for reasons to maintain their status-quo while trying to understand the mindsets of the people he knows he should think of as enemies. In game, he flip-flops a lot between belittling the Machines and respecting them as people, and it looks like this mental tug-of-war is why.
-In the prologue,
he saves 2B out of a sense of duty, but he also gets the inkling that self-sacrifice for 2B's sake is a good thing. This seems to tie into his previous lives as portrayed in Concert Script 1. In Concert Script 4 (I think), 9S was able to recite 2B's dialogue when she tries to tend to him in the Prologue pretty much perfectly when she herself gets injured. So, I still think he has impressions from previous lives in his subconscious or something like that. When reviewing the prologue, it turns out Pod 153 is actually in charge of wireless memory uploading, so whether or not he remembers anything after death seems to be on her.
-The strategy guide claims that 9S still contracted the Logic Virus during the Backdoor attack, but it seems to have grown within him slowly. I assume attaching 2B's arm to himself sped it up. I also guess that, even though he was able to halt the Backdoor update for 2B and himself, he wasn't able to get rid of it all and just slowed its growth, like how 2B was functional for a while at the beginning of C. Also, it was turning his brain to scrambled eggs by the end of the game, making managing his contradicting thoughts and intense emotions difficult. (I guess that effect is also why a lot of infected YorHa start giggling, etc.)
-His mentality is pretty nicely summarized in this passage:
Those complicated and conflicting emotions and thoughts of someone caught between the gears are part of why I think going into 9S's mental space is interesting. Also, his name is derived from "Nein ist", so I guess it makes sense for his thought process to go completely nihilist.
-Also...9S IS A BIG, OL' SUB.
IT'S CANON.
A2's Side:
-A2 is also a very interesting character. I already thought she was great 'cause of the YorHa stage play and Concert Script 3, but getting a window into her thoughts and motivations, even if they turned out to be selfish, makes me appreciate her character more.
-Even though running into Pascal and his village convinced her that Machine Lifeforms can be good, seeing the faces of her dead comrades when she fights Auguste is all the reason she needs to wipe him and Friedrich out.
-When hacking 9S in Ending C, A2 transferred the Logic Virus to herself. (By touching his face, I guess.) Looks like she planned to end the Logic Virus, the Machine Lifeforms and herself in one fell swoop. I didn't know just by looking at her, but upon reviewing ending C, it
is suspicious that you don't see her eyes after she saves 9S and it
does look like her eyes have a reddish tint to them when she looks to the sky at the end.
-A2 says "sorry" because she knows about the Machine's Lifeform's human potential and that they have created an Ark to escape the endless war, she still chooses to destroy the Ark and the Machine Network.
Looks like she wanted to fulfill her personal duty to destroy all Machines and join her friends to the end, even if her understanding of Machine Lifeforms changed. So... even though it looked like A2 had her head screwed on tighter, her actions turned out to be as destructive as 9S's. She wanted to reunite with her dead friends, but she chose to destroy the Machines (humanity's heirs) rather the remnants of the human genome left on the moon. Same drive, different sacrifice.
-In this light, her surviving in ending E might actually be something she wouldn't want.
(((
Anyway,
a full length novel is going to come out by the same person who did the Memory Cage/Thorn. I don't know how much else you can add from 9S's and A2's POVs, since we already have the concert scripts and this strategy guide...but I think 2B thoughts and feelings definitely needs more elaboration.