Anyway, these are just rough translations of what other people have commented, not my own words, thus I can't vouch for whether they are true or not until I get the novel myself.
• Naked Nia in Simon's coat has been eliminated (she still appears as the Messenger, Simon continues wearing his coat)
• The story flow is the same, but some things are abridged and developments have been changed. Every important point is depicted in detail.
• Nakim's father is actually...
• Zoushi's past is revealed
• You can really understand Makken's love
• There are new developments. The battle scenes got me really fired up. But the area around "I will never forget~" was honestly quite...harsh. I could barely read it through my tears.
• There is description of the seven days before the wedding, and I thought it was very Nia-esque
• You can see a dripping wet Yomako-sensei
• For people who like Kittan and Viral, you won't lose anything by buying this
• It was a good change for Simon to pass on the Core Drill to Rossiu instead of Gimmy.
• Lagann delivers the final blow to the Anti-Spiral that crushed Space King Kittan
• On his travels alone, Simon digs wells.
• The 4th arc battles had various changes and additions, but everything after the defeat of the Anti-Spirals is depicted simply. The return to Earth, the wedding, and what happens after is only 10 pages overall.
• I'm interested by how the novel gives a hint that Viral might have Spiral Power. Though in the end it's kind of indefinite.
• Alternate world Simon is shown in the illustration, and his feelings are written in detail, so his feelings of "I'm happy just because my bro Kamina is with me" are really communicated
• Mr. Walking Officializer is too unfair. "I'm happiest when I'm eating with Aniki"... Simon-kyun... You could be more selfish you know...you're too noble, you angel.
• It seems you CAN bring a person back to life, but using Spiral Power to mess around with life and death is frowned upon
• The star glasses are not mentioned in the writing, though they are shown in the illustrations. (Actually, both the star glasses and goggles are used in that illustration.)
• As an enemy that you can't surpass unless you blow up your comrades along with them, the Anti-Spirals' strength is better written than in the TV version. But how it stinks of a clearance sale is worse than in the TV version...
• Really? I think that in regards to the way they died, it was considerably better than the original. Zoushi, Airac, Kidd, Barinbou...making all five of them die laughing was good.
• It's been one year since the broadcast ended, and I've even watched the DVDs many times, so I didn't think that I would shed the same tears that I did when I first saw it. I've watched the anime so many times, but reading the novel I was moved to tears all the way to the end. My tear glands burst in the part from episode 24 to the final episode. The emotions from my first watch were resurrected. Because of the fact that it is in writing, the depiction was just too good... Also at the end, my tear glands burst again. I already knew it, but Simon continues to dig holes forever after all.
• The direction is different at various points from the TV version, so it was worth reading. The kind of descriptions of emotions and detailed explanations that you could only have in writing are incredible. If only the first and second novel could have been written with this quality. I wish Mr. Walking Officializer could just rewrite them. With so much Spiral Power to spare, he ought to throw that into Lagann-hen.
• I get the feeling that Viral's depictions are increased in the novel. His sweet dream has been supplemented (thanks to the Walking Officializer).
• Like Viral's negotiations with Leeron and how he shows respect towards the Helix King~
• The parts that we usually nitpick in this thread were picked up and complemented. Like why Viral is suited to being Gurren's pilot. I burst out laughing in spite of myself at the line "Oh man, he's defeating the enemy just with fighting spirit."
• And how we used to say that even if reviving the dead isn't possible, maybe they could have done something before Nia disappeared. But once she's already disappeared except for her ring, then at that point it's just impossible. Or rather, with how she resurrected and then furthermore hung on for one week after that, Nia tries too hard.
Also, I asked a question on the main thread: "Back when the 3rd novel came out, some people were complaining about the lack of insight into the female characters' thoughts, so how was it this time?" The answer I got was "Yoko's was to a reasonable level, the sub characters were to a sub character level. As for Nia, rather than how she saw things herself, her character was depicted more from the points of view of the people surrounding her." Hmmm...I guess that's a bit disappointing; I would have liked to see into Nia's thoughts more. :(
And about what that person said about Nia disappearing once and resurrecting herself...I'm not going to speculate too much on that until I read it myself, but...so is it like Nia briefly disappears immediately after the Anti-Spirals are destroyed like she ought to, and then comes back using fighting spirit long enough to get married? Zombie!Nia? Because yeah...if she's already dead, then you can't use the argument that they should have done something to save her during that one week, because that would be bringing the dead to life. Even though Nia's technically already done that for herself, at least for a short amount of time? Hmm. Well, it's not really anything new (I'd already suspected as much), but it at least makes the situation clearer for people who had trouble understanding why Simon didn't save her.
Nnnngh, I really want to read it~~~ x_x
EDIT: "Having only the ring finger of her left hand with the ring remaining is light horror"
O_O Okay, I might have interpreted the disappearing thing wrong. That's...kinda creepy, yeah. Come to think of it, I think Nakashima said something like that at an event once, about how Nia would start losing body parts if she held on for longer than a week...
EDIT 2: "Boota turning beastman never happened" :O!!