The Castle of Otranto, by Horace Walpole, 1765
This is believed to be the first Gothic Novel. While not particularly frightening by today's standards, it is still intriguing, and it's influence can be felt in many gothic novels that would follow. It involves ghosts, a giant, a love triangle, and inexplicable events. The story begins with what is still one of the most uncanny opening scenes in literature. Manfred, lord of the castle believes in an ancient curse. The curse oddly states that once the castle becomes "too large for it inhabitants", it will fall back into the hands of its original owner. Manfred interprets this to mean once the family has become to small for the castle, then they will fall out of the favor of destiny. So he has arranged a marriage between his son Conrad and the reluctant Isabella. Then suddenly a gigantic knights helmet falls from the sky, killing Conrad. Manfred then decides he will marry Isabella himself. Manfred explains as of this hour...