UPDATED: I went back and read more of this manga after dropping, and I am currently up-to-date. I am glad that I revisited this manga.
The first few chapters set the story which is a very strange one. An octopus like alien creature who can move at mach 20 speed and will destroy the world in a year will... teach a classroom for school. The goal of the manga is to have his students assassinate him. Do not be fooled by the first few chapters which appear to follow a generic "each student gets their own chapter" type of thing. The story progresses nicely, new characters come into play, and what would seem like an undevelopeable plot turns into a nice shounen manga.
This manga is not groundbreaking in any way in my opinion, but it is a fun read. I find myself liking all of the characters. Many of them grew on me over time, which is an impressive feat. To be able to set someone up as a hateable character, but make them likeable a few chapters later is tough to do.
I would definitely recommend checking out this manga if you are looking for a goofier, lighter, shounen read. I did not spoil anything in this review, but there is much more that meets the eye with this manga. If you try it out, give it 15 chapters and see how you like it. Many other people seem to enjoy this much more than I do. Give it a read, I dare you.