How much do you want to be spoilt? =D
There are altogether 235 chapters for the whole series. As to how many episodes this anime adaptation will get, it's up in the air as there is no indication anywhere. If they plan to go all the way, it can easily hit 50 episodes. That being said, do take note when the usual sponsor screens comes up after the OP and ED, they are empty
So, it can mean 13 episodes or up to 26 episodes.
I do think there's a good bit of incentive and budget for the show. Look at the production. They even roped in live action actors to become seiyus as well as getting well-known seiyus involved. Heck, they even got Megumi Hayashibara just to do the narration.