I'll second Psycho.
I'm not sure if it fits but I would like to nominate "The Castle of Otranto" by Horace Walpole.
Plot Summary (Wikipedia)
The Castle of Otranto tells the story of Manfred, lord of the castle, and his family. The book begins on the wedding-day of his sickly son Conrad and princess Isabella. Shortly before the wedding, however, Conrad is crushed to death by a gigantic helmet that falls on him from above. This inexplicable event is particularly ominous in light of an ancient prophecy "That the castle and lordship of Otranto should pass from the present family, whenever the real owner should be grown too large to inhabit it." Manfred, terrified that Conrad's death signals the beginning of the end for his line, resolves to avert destruction by marrying Isabella himself while divorcing his current wife Hippolita, who he feels has failed to bear him a proper heir. However, as Manfred attempts to marry Isabella, she escapes to a church with the aid of a peasant named Theodore where Manfred cannot touch her. Manfred orders Theodore's death while talking to the Friar Jerome, who ensured Isabella's safety in the church. When Theodore removes his shirt to be killed, Jerome recognizes a marking below his shoulder and identifies Theodore as his own son. Jerome begs for his son's life, but Manfred says that Jerome must either give up the princess or his son's life. They are interrupted by a trumpet and the entrance of knights from another kingdom who want to deliver Isabella. This leads the knights and Manfred to race to find Isabella first. Theodore, having been locked in a tower by Manfred, is freed by Manfred's daughter Matilda. He races to the underground church and finds Isabella. He hides her in a cave and blocks it to protect her from Manfred and ends up fighting one of the mysterious knights. Theodore badly wounds the knight, who turns out to be Isabella's father, Frederic. With that, they all go up to the castle to work things out. Frederic falls in love with Matilda and he and Manfred begin to make a deal about marrying each other's daughters. Manfred, suspecting that Isabella is meeting Theodore in a tryst in the church, takes a knife into the church, where in fact, Matilda is meeting Theodore. Thinking his own daughter is Isabella, he stabs her. Theodore is then revealed to be the true prince of Otranto and Matilda dies, leaving Manfred to repent. Theodore becomes king and eventually marries Isabella because she is the only one who can understand his true sorrow.
Manfred is an usurpator who wants to consolidate his reign over Otranto. So he tries to marry his weak son to Isabella, heir to a more legitimate prince. But there is an old prophecy which warns against such moves, and the day of the wedding a gigantic iron helmet falls over Manfred's son's head. Then, a creepy -mostly funnily creepy- tale develops. But the plot, though wild and entertaining, is the least important thing about this 1764's novel.
The really attractive, entertaining and literarily important thing is the creation of stereotypes: the foul weather; an ancient, dark castle full of closed halls, secret passages, corridors and doors; frightening apparitions; wicked tyrants desperate for fertile women; virtuous and pure ladies; heroic lads; dark and cold forests where ghosts appear, etc. Walpole, who seems to have been an interesting man, must have had enormous fun writing this tone-setting book, which has had plenty of children in literature. When I read it I kept imagining the scenes, the settings and the weather, and it was great to imagine it come alive. Literarily imperfect, it is fun to read and to discover where many of the commonplaces in Gothic literature come from. Well worth it.