The first chapter I thought was just okay; episode 22 is one of my favorites so I'm already biased, but experiencing it in writing didn't excite me as much. There were some changes in how the battle played out, but mostly it was the same. Actually, I kinda felt like there was too much dialogue. As in, a little less instinctive action, and a little more "oh look at the data that just popped up, let's try this out!"
The second chapter was more enjoyable because of all the characters interacting together. I especially liked how Gimmy was a little resistant to seeing Viral join them, and Simon having to explain why he's best suited to being Gurren's pilot. I loved Rossiu's thoughts and his conversation with Magin, but I already spoiled myself for parts of it so it didn't come as much of a surprise. Overall, this chapter is mostly the same as the anime too and I was starting to get bored.
So, although I'm probably ruining my own reading experience by spoiling myself again, I skipped ahead once more to read bits of Chapters 3 and 4.
Holy shit. THIS IS SO GOOD. SO GOOD. *___* I'm seriously having trouble making myself go back to Chapter 2 again. I'm also tempted to translate all of this once I'm done so I can share my squee, but I don't know if I can just pick certain excerpts because it's all so good and I can't decide when to start and stop. Plus I already know Chapter 5 is awesome too so all together that's like 2/3 of the entire book. Guh.
Anyway, here are some spoilery details that I just have to gush about. A lot of these really seem to improve parts of the 4th arc that people usually nitpick over:
-Viral is no longer useless! At one point he actually saves everyone because he's the only one without Spiral Power ahaha. Totally badass. *_*
-Because Kittan gets seriously injured early on, he and Yoko get more interaction. I noticed that one of Yoko's lines to Kittan from episode 25 of the anime got moved to Chapter 2, before they even set out for battle, so their later dialogue reflects back on that. And as I'd hoped, Nakashima used Kittan's development in the 3rd novel to help build their relationship. Also, Kittan's injuries mean that he's already on the brink of death when he goes to sacrifice himself. BAD. ASS.
-The other Gunmen pilots' deaths are much more of a willing sacrifice, so they don't just get killed off pointlessly. And the way it happens makes me want to cry, those people weren't lying. ;___;
-Speaking of which, you know how in the beginning of episode 26 of the anime it looks like Simon is crying blood? HE ACTUALLY IS CRYING BLOOD. Not just tears that look red because of the star glasses. BLOOD. Simon also coughs up blood and falls unconscious while powering up the ship. Holy shit.
-Nia is portrayed as having more of an active role even while she's held captive. Yoko has awesome internal monologue about wanting to save Nia as a friend. And Simon is so pissed at the way Nia is being treated by the Anti-Spirals that he has to keep from expressing his anger out loud or he fears that he'll lose control of himself completely.
-Lord Genome character development omg. It's actually pretty cheesy but omg. I love it.
-AU!Simon and the ring omg. Once again I want to say STFU to the complainers in the Nia thread because seriously. There's Simon/Nia all over the place. *_*
-OMG. There's no Kittan/Yoko wedding scene, but in the Bounty Hunter Yoko parallel world, Kittan is a former bounty hunter now turned Chief Inspector of the Littner police force. He and Yoko flirt and snark at each other over the phone and it is AWESOME. *_*
EDIT: I know I'm probably being annoying for posting so much about just one book. It won't last too much longer, I promise. >_>;