I normally don't structure comments like this, but this is honestly such a wild ride I'm not sure I could be coherent otherwise.
Art: 8/10
The ... expressions are magical. Especially those with tears.
That is to say, they all look pretty silly.
However, I dig the old style, and the mangaka sure knows how to do a full page spread. He's got an eye for detail, too.
Plus, some of the character designs are fairly imaginative.
Characters: 5/10
Little to no character development.
Very few of the characters' reactions or actions are believable and they make leaps in logic I wouldn't previously have thought possible. It's unintentionally hilarious, occasionally infuriating, and to clarify, this happens every couple of chapters or so.
Bizarrely, toddlers past a year old or so can speak/understand language perfectly and grasp otherwise difficult concepts to swallow/ Honestly, they probably behave the most logically out of the entire cast.
Plot: 9/10
The series is structured into arcs, and there is no transition between them. Initially, this is fairly jarring, but you get used to it. There is an overarching plot although the mangaka takes a while to set up the story before reaching it. Without giving away too much, the plot is incredibly unique, refreshing, and fairly well-written.
Most of the arcs seem to be connected in ways that are planned, which I appreciate, but it's fairly obvious, at least to me, when they aren't (you'll find a few continuity errors).
Writing: 6/10
There've been a few continuity errors and plot holes from what I've read so far (ch. 183), mostly relating to characters switching pronouns. I'm not too sure if it's due to errors on the translator or mangaka's end, but I suspect the latter. It's a little distracting, but mostly minuscule.
I wouldn't really call this horror, as it's neither particularly frightening nor suspenseful. Every arc or so, the mangaka seems to remember the genre and draws some gore that, quite frankly, feels out of place.
I'm not sure I'd consider it sci-fi, either, as that normally has some grounding in reality, while this just page upon page of misinformation, and none of the futuristic technology is ever explained in detail. That is, it's fairly shoddy world-building for sci-fi. You do get a few hilarious anachronisms from the 90s (brick monitors, computer punch cards).
Misc: 10/10
All flaws considered, I'd still read this if I were given a chance to do this over. I had fun reading this, and I've got some priceless reaction images in my folders. 14-sai is honestly best read with friends, so everyone has the opportunity to go, "what the heck?" and "how did you come to that conclusion?" etc.
This manga is a wild ride all the way through, and yes, I'd recommend this to someone without hesitation. It's the weirdest thing I've ever read, and personally, I think that says a lot.
I started reading this because of the strange premise, because I like body horror, and because I like chickens. It really doesn't disappoint. Just let the events unfold as they may; laugh if you must.