So I went back on something that physically looks more like a book - so the object is immediately recognized as a “book” by visitors, and there's no additional cognitive hurdle.
Having said that, I want to have some weight associated with the book, and still have a slightly industrial effect. So, for the cover, I've been inspired by the buildings - particularly the Hub and Container in the game - and I'm proposing to start with a Satisfactory yellow/orange leather/faux leather cover (depending on the colors I find), and to reinforce this cover with a light black aluminum structure.