Sidonia no Kishi is an excellent work by Nihei Tsuomu.He has improved his style, adapting it to the more usual manga style but still keeping his lines and proportions.
Nihei uses the "Gauna" from other works(Creatures able to change the outer layer of their body into armor,limbs,weapon, etc.).
The main character, Tanikaze Nagate, is a quiet guy who is confused from the new world that he has discovered.It seems that he will have to choose between two girls(one being from the third gender-not male nor female).
The Gauna is a very powerful race nearly indestructible, but they can be killed by using a special spear on their exposed body.
Overall it's an excellent manga, very good art,very interesting background and an open plot witch keeps you wondering