A is for Azazel, any child could tell you. B is for Baal, C is for Caim, D is for... ah sorry, this isn't The Big Book of Demons. Right! The regular-sized Book of Demons [official site] is a deck-building action-RPG with a papercraft style, and is currently on Steam Early Access. It's still a while away from release but if you fancy a crack at duffing up monsters with the help of cards for special abilities and items, hey, it now has a demo.
So! Book of Demons sends your fightmen down into dungeons to bash monsters, which very superficially looks a bit Diablo-y. You click on monsters until they explore into showers of coins, sure, but you also collect cards representing abilities, items, and so on. You can only have a few active in your 'card pane' at once, with those not equipped being useless to you. It sounds a bit like making Diablo ability and item be the same type then limiting how many you can use, which is an interesting build-making proposition. I'll need to have a bash when I have a free mo.
Here's developers Thing Trunk playing through the first half-hour, tutorials and all, as a Warrior - the only class in the game so far (more are to come):
For folks who played it before, hey, Thing Trunk have also launched a new update making the higher difficulty levels more challenging.
Book of Demons is £14.99/19,99€/$19.99 on Steam Early Access, which is where you'll find the demo too. Thing Trunk plan to launch Book of Demons properly either at the end of this year or early in 2017, after a bit more polish and a few more additions.