Volume 1 was interesting, as we've all seen.
Volume 2 was boring.
Volume 3 was like, WTF?
Volume 4 was like, WTF times infinity.
I think this was a case of the author not know where to go with this.
This page near the end summarizes the manga pretty well.
Spoiler
Edited by ThunderCloud, 16 October 2013 - 08:35 AM.