Cthulhu Dark is my rules-light Lovecraftian game. (Or try the easily-printable version).
The rules are fun and incredibly minimal: they fit on one sheet of paper. You don’t need a character sheet to play, so you can start playing after two minutes of prep. Despite the simplicity, there are some interesting rules twists: look at the Suppressing Knowledge rule for an example.
More info here from Thieves of Time. Just about to print it out.