Solved
Sims keep holding invisible book after putting it down
Sims 4, sim reads a book, puts book down on table, floor, book shelf, etc. appears to be holding the book in an empty hand. Cannot do any other actions that require that hand or two hands such as was...
The hand thing you are seeing usually happens when there is no accessible bookcase or a storage chest/box nearby. I see no bookcase object in your pic. If you are using one of the small surface mounted bookcases (looks like a row of books with bookends) and it is sitting on something like a dresser, you might get the hand thing and a routing error because you can put those small ones in places where sims cannot put books back in them. Those don't work right on every surface like dressers and some desks for some reason. You can get books out but not put them in. As you said, you can reset the sim to get the empty hand thing to go away but you can also travel or save and quit and reload the save.
Hope this helps.
