https://techraptor.net/content/binding-isaac-afterbirth-emerges-january

- 1 new chapter+boss
- New Character
- 60+ new items

For 6.66 (yes) if you already own afterbirth. I've played this since the first demo on newgrounds, and I'm still excited to see another expansion coming.

I hope Edmund finally fixes The Keeper so that he may nto be viable but not complete suffering to play either.

Wiki lists it as:

67 new items, 27 new trinkets, and 10+ new pickups
4+ new bosses, a new final boss, and new alternate forms of existing bosses
2 new transformations
A new character, Apollyon
Hundreds of new rooms
New monsters and champion variants
5 new challenges
40+ new achievements
New final chapter
Hard Mode for Greed Mode
Daily Greed Mode runs
A bestiary that shows detailed information about monsters
A "Victory Lap" mechanic; players who have beaten Dark Room can start over with all their items intact and increased game difficulty[1]
Various features for modding support, including:
An item pool editor
A room editor
An animation editor
Lua support
Custom challenge creator
A monthly update to the game implementing the best mod into the game, permanently.

What an absolute madman