When I want to run an adventure about unknowable horrors, 1930s investigators in over their heads, ancient books that send readers insane, and all that squirming Lovecraftian goodness, there's one TTRPG I reach for every time: Trail of Cthulhu.
Its clever system puts the emphasis on solving mysteries, giving players all sorts of tools to discover clues and learn more about what they're up against before confronting whatever horrors await. The feel of it is perfect for the genre—dread mounting as the players uncover more and more disturbing evidence, but at the same time always being tempted forward into yet more forbidden knowledge.
