Volume's 9 arc is a good place to stop at.
My main problem with the manga early on as said by others it's basicly "monster of the week". It kinda got old pretty fast. But it better a bit later on when it sorta moves beyond that.
Especially with the whole
Anyways the characters are likeable including the main character. Hopefully the fight scenes are better done in the anime because early in the manga they were rather plain.