The World of Bloodshadows is a setting for use with the MasterBook rules system.
From the back of the World of Bloodshadows boxset:
The World of Bloodshadows is a roleplaying game setting that combines pulp adventure with dark fantasy. Tough detectives in weathered trenchcoats swap biting comments with vampires in evening gowns. Humans walk down dark streets side by side with demonic breeds and long-dead ghouls. And death - or Undeath - waits around every corner.
Go outside the cities and discover the terrors of the Wilderness. Even the most powerful shapeshifter or sorcerer fears what waits in the ruins...
Your weapons in the world of Marl are magic and technology - but neither replaces a good head on your shoulders.
And you'll have to work to keep it there.