On the cover: A fantasy noir setting for Mean Streets, requires the use of Mean Streets
From the introduction:
That Old Black Magic is a freebie supplement for Deep7's role-playing game of classic film noir Mean Streets. Veering slightly to the left of the game's default 1943 setting, Black Magic presents an alternate setting for the game, incorporating sorcery against the backdrop of 1940s Hollywood. It's a world where gangsters in expensive suits are master sorcerers, spirits get the third degree from cops, zombies come six to a crate just like bon-bons, and your landlady is a licensed witch.
Black Magic gets its influence from films such as Cast a Deadly Spell, Witch Hunt and other role-playing games, specifically West End Games' Bloodshadows. Don't take the setting too seriously, though, as it was written tongue-in-cheek and meant for a little light-hearted change of pace, interjecting a bit of Hollywood magic quite literally.