Today's the last day for the kickstarter. When the game comes to stores next year, it will be more expensive than it is in the kickstarter, so now's a good time to buy if you have any interest.
They've also added some goodies exclusive to the kickstarter. All tiers are going to get a few extras like a post card and stickers. Of course going up from the base levels you get even more exclusives.
I have a friend who's into Isaac and tabletop games so I was able to split the 2 box option with him which saves even more money.