I just finished reading the original novel Frankenstein which Mary Shelley published way back in 1818. I've heard some consider it to be the first science fiction novel ever written.
It is a literary masterpiece, and an intense page-turner. If you have not yet read it, you may wish to set aside any preconceived notions derived from the the Boris Karloff movie; the book features no spooky castle, no hunchback named Igor, and no flat-headed monster with electrodes in his neck. In fact the movie resembles this book no more than it resembles Edward Scissorhands (another story I love).
I enjoy the classic movie, but the novel is far grander and deeper... and scarier. It takes the reader on a tour through all of the negative emotions, not just fear but grief, depression, guilt, desperation, disillusionment, and hatred. All of these emotions are portrayed in a disturbingly convincing manner. Joy is portrayed too, but joy is always destroyed by grief that follows.
Having been written during the romantic era, the characters often speak in a formal, poetic manner that may seem melodramatic to modern readers, but the dialogue is often beautiful if one looks past the fact that real people don't actually break into flowery monologues in casual conversations.
Short Summary (SPOILERS!):
Victor Frankenstein experiences an idyllic childhood in Switzerland, surrounded by a loving family and accompanied by his adored cousin Elizabeth. He is fascinated by ancient philosophers whose grandiose ambitions included looking for an Elixir of Life. After the death of his mother, his first unhappy experience, he attends University in Germany where he applies his new-found knowledge of science to manufacture a human being of enormous size and strength.
When his creation comes to life, Frankenstein is so horrified by his own bizarre accomplishment that he falls into a delirious illness which last months. Meanwhile, the creature flees into the woods and disappears.
Two years later, Frankenstein returns home upon learning that his brother has been mysteriously murdered. Justine, a friend of Frankenstein, is falsely convicted and executed.
Having been hated, rejected and feared by every human encountered, the creature considers all of humanity to be his enemy. He demands that Frankenstein create a female companion for him so that he will not be lonely, and promises that with his companion he will flee to a remote corner of South America and never come into contact with humans again.
Frankenstein cannot forgive the creature for the death of his brother and Justine; he refuses to build the female companion. In desperation and rage, the creature promises to make his creator as miserable as himself. In his vengence, the creature murders Frankenstein's friends and family one by one, including his beloved cousin Elizabeth (who he married; 19th-century writers apparently weren't too bothered by incest; Wuthering Heights featured inter-cousin romance as well).
When the creator and his creature are at last equally alone and family-less, Frankenstein seeks his own revenge and pursues his enemy into the Arctic northern wastes where together they meet their climatic fate.
Pretty cool, huh? Okay, that summary doesn't do the book justice, but I hope it conveys that the scope of the story is somewhat greater than that of the 1930's movie and its sequels.