You might look at this and say wow, it looks pretty good not to mention the artwork looks amazing!
But holy Christ I can write a paper on why I hated the story (and how the ending completely ruined everything for me).
I'll save that for the last part because I can rant on that forever.

Art:
It looks great, down to earth and rather realistic in some cases. The detail goes down hill a bit for me as it continues on but overall it's rather great. Not the best as it tends to get sloppier in fights or even towards the final few chapters. It isn't the most beautiful, but it isn't horrendous either. Bonus points since I like Mecha.

Characters:
They have good flow and interaction with each other as time goes on, and the impacts they have on each other is very great. The MC with his first love interest was great, and throughout the entire story made sense why he was so focused on here. Even if it was obsessive at one point. The characters feel somewhat alive with the doings and personality. Later on, towards the ending, the MC's obsession with his first love interest in my opinion goes way too far. I'll touch up on this in the story section of the review, but overall most of the characters don't seem too bland or awful.

Enjoyment/story
"Why did you give enjoyment a 10 outa 10 if you rate it so poorly? Then give the story a 1/10, what's up with that?"
This ending of Sidonia no Kishi is the biggest joke I have ever seen. I remember being excited to continue the story, wondering where it was going. Then, it started to take a turn for the worse. Where my enjoyment started dying out because the story WAS a gritty story, those who are dead remained dead etc etc. There was no dues ex machina like anything I've seen in this ending. All the love that the MC puts into the secondary love interest and all their interactions and the secondary character's eventually decision to love him is COMPLETELY THROWN OUT IN BASICALLY ONE CHAPTER. Not only that, but a person who was (and by all regards should be) dead comes back to life for the MC to screw and have kids with. Which, as stated in the story, was biologically impossible. Did I mention that the thing he screws is basically his daughter?
Yeah, I'm not screwing with you.

In my opinion, this manga is great until the introduction of the "daughter-like" character and the final "dues ex machina" like character in the final chapter (I believe, I had to legitimately purge this story from my mind it angered me so much.) It was great, and semi-realistic while being entertaining. The ending however, ruined what I had loved about the story so much. It had killed all enjoyment I had in the story because of it, and two characters who clearly were dead had suddenly come back to life marked the final disappointment for me. It felt as though the Author needed to come up with this to please the Shipclubs or something, because it came so out of left field and awfully compared to every other part of the story.

To sum it up, read about all the chapters until the final battle. At that point, imagine your own ending because it is almost guaranteed better than what I read.

The ending is that bad, I am not kidding you. It was great until the horrible cop-out ending that was not only DRAWN with very little effort, but also dialogue with very little effort. It's like an M Night Shyamalan movie, another man who cannot end a story to save his life.