A classic example of gothic horror, Mary Shelley's Frankenstein represents an important work of science fiction, much more so many other works of horror produced before or since. Frankenstein is an astonishingly serious exploration of discovery grounded in philosophical discussions regarding the role of morality in science. That it can be considered "extraordinary" is a product of the "fictional" component of a work of science fiction.
In the story, Victor Frankenstein becomes fascinated with the idea of regenerating life from the lifeless form. He becomes obsessed with the idea of bringing dead tissue back to life, eventually succeeding at bringing a dead worm back to life, and is encouraged by his success in that experiment at attempt the same thing with a dead human -- something not accomplished almost 200 years after Frankenstein was published. The ambition, considered by Shelley almost 200 years ago, is extraordinary in itself; that the author presented the story in such a thoughtful or reflective manner speaks to her own extraordinary abilities as a writer. As Victor himself exclaimed following his success with the worm, "I succeeded in discovering the cause of generation and life; nay, more, I became myself capable of bestowing animation upon lifeless matter."
Beyond his scientific prowess, Victor becomes caught in what we would today call "the God complex," the conviction that one possesses powers over life and death second only to the Creator: "Life and death appeared to me ideal bounds, which I should first break through and pour a torrent of light into our dark world. A new species would bless me as its creator and source; many happy and excellent natures would owe their being to me."
Victor Frankenstein is an extraordinary man, and his drive to bring the dead back to life represents an extraordinary quest.