Lovecraft Letter is a card game that combines the Love Letter system with the world of H.P. Lovecraft. In addition to the standard sixteen cards in the Love Letter game are new versions of the cards that include special "insanity" powers. If you have one of these cards in your discard pile, then you are insane (at least for the current round) and on future turns can play insanity cards for their regular power or their special power, giving you more options during play. The risk, however, is that you must undergo a sanity check at the start of each of your turns, drawing as many cards from the deck as the number of insanity cards in front of you; draw one or more insanity cards, and you're out for the round.
Don't just take our word for it! Check out this review of Lovecraft Letter.