Ah, so you found the Fantasmagoriana too? Yes, I came across that two days ago in an article I was reading about Polidori (“Dr. Polidori and the Genesis of Frankenstein” by James Rieger). Rieger suggests that there is only one extant copy of this book in the US, and that in the Library of Congress. Rieger says that Fantasmagoriana is “described by the only scholar who claims to have read it as ‘a poor sort of book'” (466).
And this is a exciting connection, too–but, then, if this were the whole story, why Polidori and not Mary Shelley, who is the one who gives the account of Fantasmagoriana? After all, Frankenstein is a much better known book, and also has themes that resonate with the game (as well as an interesting layered narrative structure, as Phantasmagoria has in a different way). My strongest hypothesis so far centers on the relationship between the Byronic Lord Ruthven and Aubrey (who is generally taken to represent Polidori). I suspect that the presence of this book means we’re to read Carno as a Byronic figure, parallel to Ruthven, but this hypothesis needs a lot of refinement still.
These are interesting articles you found; they present a very different perspective than the ones I’d been digging up in literary journals, even though the basic sources and details are the same. Thank you!