Absolutly one of my favorite games. A combo of mutiple items, random dungeon generation, and mutiple characters gives this game hundreds of hours of playtime. It is quite hard until you get used to it and some of the unlocks are hard to the point of being unfair. Still I wholehearlty reccomend it.

As for the DLC

Afterbirth takes an already great game and polishes it to a mirror shine. Great new items and features. Get it

On the other hand Afterbirth+ is harder to recomend. If you are an Issac nut like me or greatly enjoy mod support I would get it, but its quality is significantly worse than afterbirth. It is also significantly harder in the wrong kinds of ways. Wait for it to be on sale or wait for more monthly content packs to be released. (Edit) Now that the community has gotten involved and the boster packs have come out I do find this expac much better than before, still not required but much improved.