Torako is not a fantastic writer. I've translated a couple other writers much better than Torako and I can tell the difference in style. Yet Torako captures one thing that's very difficult to do: characterization. It's rare for me to say "there's not a character I didn't like" but that applies to this series. S/he uses each character to the benefit of the story without over-emphasizing anyone but our two leads. Isshiki serves well as the perverted best friend and support. Shy Mode was a funny surprise to me and I enjoyed phrasing those lines. I mentioned my thoughts on Nibutani earlier, but now I can go into depth. On the surface, Nibutani hates chuunibyou (the disease). That doesn't mean she hates the people infected with it. I enjoyed her "villainy" until the middle of chapter 8 when I realized that she doesn't wish ill will on the people; she truly cares about everyone and doesn't want people to regret their past. Much different than the anime version of her character. Nana-chan doesn't get to shine as much as she does in the anime, but I really liked her opening appearance mocking the people who did poorly on the test. Finally, my favorite character at the end of the novel is someone who's been looked over in the anime: Kazari Kannagi. I loved her appearance in chapter 8; it really made an impact on me. I really wanted to see more of her in the novel/anime, but alas. (She's the purple-haired girl near Yuuta in the anime)
Plot-wise, you'll see a huge change at the beginning of the first chapter: Yuuta's already crushing on Rikka and Rikka alone. I've seen so many rumors that stated "it's a love triangle in the LN." I laughed everytime I saw someone say that. Going back to a lot of Ishihara's comments, you can see why he kept emphasizing the romantic part of the story: it's so prevalent in the LN. They amplified the chuunibyou aspect of the show (seriously, you get one "battle" in the novel) and are just now focusing on the romance whereas the romance starts in chapter 1 of the novel. Again, you'll see why I kept saying "they're two different worlds." At the same time, both exceed in what they're set to do. The novel works well to tell the story in text form, but the anime exceeds in their visual story-telling. Now if I could stop Yuuta from embarrassing himself (and actually spell that right on the first try), I'd feel better. It's not the most complex story, but the use of a test to bond the two is done alright. Yuuta/Rikka help carry the story to become better than what it sounds like.