Of all the books in all the world that have been inspired by dreams, Frankenstein remains the most famous. (Though Twilight did what it could to oust that.)
In the introduction to the 1831 edition of Frankenstein, Shelley goes into detail about the inspiration behind the novel: her nightmare.
“When I placed my head on my pillow I did not sleep, nor could I be said to think. My imagination, unbidden, possess and guided me, gifting the successive images that arose in my mind with a vividness far beyond the usual bounds of reverie. I saw — with shut eyes but acute mental vision — I saw the pale student of unhallowed arts kneeling beside the thing he had put together. I saw the hideous phantasm of a man stretched out, and then, on the working of some powerful engine, show signs of life and stir with an uneasy, half-vital motion. Frightful must it be, for supremely frightful would be the effect of any human endeavour to mock the stupendous mechanism of the Creator of the world. His success would terrify the artist; he would rush away from his odious handiwork, horror-stricken. He would hope that, left to itself, the slight spark of life which he had communicated would fade, that this thing which had received such imperfect animation would subside into dead matter, and he might sleep in the belief that the silence of the grave would quench forever the transient existence of the hideous corpse which he had looked upon as the cradle of life. He sleeps; but he is awakened; he opens his eyes; behold, the horrid thing stands at his bedside, opening his curtains and looking on him with yellowy, watery, but speculative eyes.
I opened mine in terror. The idea so possessed my mind that a thrill of fear ran through me, and I wished to exchange the ghastly image of my fancy for the realities around. I see them still: the very room, the dark parquet, the closed shutters with the moonlight struggling through, and the sense that I had that the glassy lake and white high Alps beyond.”
This vivid image — the one Shelley was so eager to erase by looking around her bedroom — became the “powerful engine” driving her story. Everyone who has been exposed to the story of Frankenstein — whether through children’s cartoons (thank you, Scooby-Doo), any of the film versions or — please Heaven — the novel itself — can attest to the visceral nature of Shelley’s initial dream.
And I think the vivid, visceral nature of dreams is what makes them so enticing to write about and so tricky.
Generally, lucid dreams are emotionally charged too — so not only do you have an image that’s striking (like a stitched-together corpse) but that image is tied to a strong emotion. Like terror, in Shelley’s case.
Writers should be highly encouraged to follow their dreams…literally. As a writer, you should see where those sharp imaged and super-emotional emotions take you.
But — and this is the tricky part which makes Mary Shelley a legend among hundreds of novelists for hundreds of years — the emotion/image combo should somehow feed the engine of narrative. Mary Shelley didn’t only write the scene where Frankenstein’s monster is created. All in all, that would not make a legendary story, as terrifying and visceral as it is.
Instead, Shelley creates Frankenstein as a man with deep ambitions that drive him to create this creature. So her main character’s want — his objective — is tied to the dream image.
Then she takes it a step further. She gives the other character in her dream wants — objectives — too. Objectives which are diametrically opposed to her main character. So the scene of student-doing-something-he-shouldn’t turns into a meeting of protagonist and antagonist. (Which is which? Who knows? Another stroke of genius!)
With some divine comparisons thrown in on both sides:
Frankenstein: “I had gazed on him while unfinished, he was ugly then, but when those muscles and joints were rendered capable of motion, it became such a thing as even Dante could not have conceived.”
…And Frankenstein’s monster: “Many times I considered Satan as the fitter emblem of my condition, for often, like him, when I viewed the bliss of my protectors, the bitter gall of envy rose within me.”
Everything in the story spins out from that central image of Shelley’s nightmare — the disgust, the envy.
And that’s the important thing to take away: don’t write only your dream. Because then you’re just writing images and emotions. Use those images and emotions to create conflict and drive the story.