I have just read this for the first time as I will be studying it later this year. I have a few thoughts on this moral tale, which for me was more of a tragedy than a ghost story.
One of the things I was surprised about was the fact that Shelley didn't explain how the monster was brought to life. Yes we all deduced that it was a bolt of lightening from the various film adaptations but she did not herself tell the reader this. Also, while it is obvious that Victor used body parts for his creation, I was again surprised that she didn't include descriptions of this as it seemed an important thing to include (not that I would have wanted to conjure up images of body parts you understand). Neither did she really describe the features of the monster in detail.
It was a heart breaking story, in which I had little to know sympathy for Victor but immense sympathy and compassion for the creature throughout.
It was supposed to be a tale of the Supernatural, or a horror story. There was nothing to suggest that it was to be limited to a tale about ghosts.
The mechanics of 're-animation' would have distracted from the idea of its' happening; it would have become too literal/scientific rather than a fantastical notion.
"We will each write a ghost story," said Lord Byron (Shelley ix). And Mary Shelley wrote Frankenstein (1818). But the novel is so apparently about a monster that runs amuck, that it is appropriate to ask exactly what Shelley meant when she insisted that she was writing a ghost story.
"Sitting around a log fire at Byron's villa, the company also amused themselves by reading German ghost stories, prompting Byron to suggest they each write their own supernatural tale." - Wiki
There are no ghosts in it, but when Mary Shelley and her husband were staying with Lord Byron at Lake Geneva, Byron asked them all to conjure up a terrifying ghost story. After much deliberation Frankenstein was born.
I think one of the reasons the creation of the life force is not more detailed is because it involved unnatural sexual activity (e.g. masturbation and/or bestiality) by Frankenstein - "vile practices" I seem to remember occurs somewhere in the book (some years since I read it, so may be inaccurate). The resulting self-guilt was one reason why he was so reluctant to proceed with the second specimen.
Such detail would be totally unacceptable in those times.
I have not read the novel for a very long time, so i am a bit hazy on the details.
I would suggest that Shelley did not include any detail of the use of body parts because she would not have the knowledge to make accurate descriptions, and preferred not to use her considerable imagination in this area.
At the time the novel was written, surgery was very much in its infancy, and the general populace would have no conception of transferring body parts - hence this is entirely a fictional concept at this time.
The description of The Creature is again left to the readers' immaginations, as was the standard literary tool for the genre - gothic fiction - when imagination was a more powerful took then than now, when such works were consumed by flickering candlelight while the wind howled outside - far more scary than a nice bright pc screen!!
The sympathy engendered for The Creature is the enduring strength and appeal of the novel, the heart of the compassion is The Creature, unloved and unable to love - and the more gruesome parts are justifaibly left to the readers to fill in.
The TV movie made in 1973 is excellent, well worth tracking down on DVD -
it's not a DIY manual. These days it probably would be, with every step minutely detailed, because that's the way modern books are written: realism is thought important. It wasn't then, and even by 18th/19th century standards this was intended as fantasy.