I think your understanding is correct.
Interested in Language
Even today, copies of the book have existed long after the movie and slide show ceased to be presented, and are many peoples’ only recollection of the project.
The way in which I understand the above sentence is as follows:
The movie and slide show are no longer presented, yet copies of the book have been owned by people for some time now and the same copies are many peoples’ only recollection of the project.
What do you think?
Sorry about the typos in the title.
... though there's nothing in the original about people owning the books.
No, there is no mention of people possessing the books, but we can guess that people own and read books.