Haven't seen the film or read the book, and am unlikely to, but had a look online to get some idea what the book is about, and found mentions of English colonising of Scotland, socialism, the present state of Scottish Culture, Frankenstein. It won literary prizes including the Whitbread and a Guardian one.
This book review from 1993 by an unnamed author gives a favourable view* of it and what appears to a fairly straightforward outline of the story:
https://www.kirkusreviews.com/book-reviews/alasdair-gray/poor-things/
*It mentions a previous book of his which from which he later removed a lot of the sexual content, according to an article in Wikipedia:
' "Something Leather concludes with a section entitled Critic Fuel - An Epilogue, in which Gray describes the circumstances surrounding the book's development and offers an extended ending. He comments in the Acknowledgements that the title made reviewers treat it as "a sadomasochistic Lesbian adventure story" (these events only take place in the framing Chapters 1 and 12) and that had he called it Glaswegians they might have paid more attention to the rest of the book. Indeed, when Something Leather was collected as part of Every Short Story 1951-2012 (Canongate, 2012), the collection was grouped under the title Glaswegians, and some of the stronger sadomasochistic elements were dropped.
Gray said that the novel was born out of an attempt to write a story about a woman (an idea he credits to Kathy Acker) since his previous books had been about "men who found life a task they never doubted until an unexpected collision opened their eyes and changed their habits." '
A lengthy and enthusiastic review by Jonathan Coe also goes into this:
"Here we find another contrast with Something Leather. Part of the impetus for that novel came from a suggestion made by Kathy Acker, who asked Gray if he had ever written a story with a woman as the main character. He answered: ‘No, that was impossible because I could not imagine how a woman felt when alone.’ This was a brave and candid admission. It acknowledged an inability to engage with female characters without the mediating presence of a male consciousness: for the purposes of Gray’s imagination, in other words, women are only defined, only made real, by their relationship with men. It’s for this reason that the all-female orgy scenes in Something Leather don’t come to life (except for those, perhaps, who share his particular fetishes). And this, too, is why Gray is able to enter with such gusto into the story of Godwin Baxter and his artificial woman – because it’s also the story of Alasdair Gray, the writer, and the various Rimas, Marjories, Helens, Dennys, Jills, Ludmillas, Junes and Donaldas he has fashioned out of words during his career as a novelist, sharing with Godwin the simultaneous hope and anxiety of the benevolent creator who longs to see his progeny take on an independent life even as he is loathe to forfeit his own absolute control over their destinies."
https://www.lrb.co.uk/the-paper/v14/n19/jonathan-coe/gray-s-elegy
A shorter article here by Philip Hensher, a judge on the Guardian prize panel:
"Elizabeth Young, reviewing Poor Things in the Guardian, considered it to be the "most substantial" book that he had written since Lanark. Gray, she wrote, has finally man aged to unite a number ot appar ently irreconcilable obsessions with women, fiction, politics, and Scottish history into what is a bibliophile's paradise of postmodern precision. Poor Things revives an intriguing literary torm, the medical romance. Like Doctor Jekyll and Mr Hyde, or The Island of Doctor Moreau, Gray's novel raises serious philosophical and historical issues within the engaging framework of nineteenth-century melodrama. What seems at first an amusing farrago of virtuous Scotswomen, wicked English rakes, Parisian brothels and monstrous medical experimentation, slowly shows itself to be a meditation upon sexual morality and upon notions of femininity."
-https://www.newspapers.com/article/the-guardian-the-guardian-fiction-prize/134289496/