If you watched the first episode and thought to yourself "what the heck are they talking about, nothing makes sense.." then join the club.
Story
Kyoukai Senjou No Horizon (or KSNH as I'll refer to it for now on) is a messy affair. It tries to place the histories of nations, empires, etc all into one big blob and expects you to understand it. Either that or they tried to take too much of the original work and put it in 13 episodes. Pull out those history books, you'll probably need it to understand somewhat of what's going on. Basically the story revolves around humans who are recreating history. Why? Who knows since we aren't really told in great detail. Maybe they did say something about it, but because the anime is just a mess story wise, it was hard to grab a hold of almost anything of historical value; much less the story. In the end it's basically, boy meets girl, girl dies/goes away, boy decides to save girl at all costs, which is something I've probably seen in so many of these animes that try to seem unique. Well maybe KSNH is unique in that it just confuses the hell out of anyone trying to understand it. I give the story a 3.
Art
Well one thing that wasn't a major let down at least, was the artwork. Although I have to say that the proportions of the characters are just extremely exaggerated. Who the hell walks around with 50 pounds of hair on their head? No one! I mean the chicks on the show sure are some hairy women with huge boobs to add! I'm surprised none of them fell over due to the weight. Even though the proportions are just plain ridiculous, the art work is very well done. Lots of eye candy. I give it a 7.
Sound
Mediocre. I seem to recall the main characters voice is the same actor as the voice of Watanuki from XXXholic (I forget his name). While he was pretty good in XXXholic, he was just plain annoying in this one. Maybe it's his character, but geez was it annoying. The only thing that really stood out to me was the battle them music, which really made it seem like you were going into battle and menacing. Great stuff, but other than that...mediocre. I give it a 5.
Characters
I can tell you one thing. The characters on this show are terrible. The main one especially. Not just his annoying happy all the time voice!, but just how plain stupid and idiotic this guy was. All he does is watch porn, yeah seriously, and he's the supposed leader of this "nation"? It's hard to take him seriously even he tries to confess his love, or when he tries to win an argument; it just plain didn't seem genuine. That was my major beef with the character. Just a poor character. The other characters? There's tons of them; and none, I might add, that really stood out, well maybe the Indian guy that shoots curry (no seriously, that's his attack.) I thought K-on had bad crappy characters...well this one might just beat it. I give it a 3.
Enjoyment/Overall
Overall, I somewhat enjoyed this for some of the few battles they did have, but I just never really established any kind of relation to any of the characters. There are just too many of them and the main lead one is just plain poor for anyone to really genuine like. Horizon (the other main lead) was just a plain doll. Not really mattering until the ending episodes which by then I just plain gave up. From what I understand, a second season is coming out and I don't plan on watching it. Seems to me like it would just be the same ole same. I'm not falling for that again (I'm looking at you K-on). Want my advice. Run away from this anime. It's just not that good. Extremely poor story telling, crappy characters, forgettable music. I do no recommend.