I have tried to save a sim with the career books in his inventory to the library and placing a copy of that sim into my household to see if the careerbooks are copied. But they where simply disapeard out of the sims inventory so I tried to copy the whole family with the bookcage holding the career books in the family inventory and copied that to the library. After I murged that family with my other family the bookcage got added to my original bookcage but without the careerbooks.
So, I can not think of another way to switch the career books through families. It seems that it is saved per city and town or so, not per save file apart. Anybody who can come up with good ideas?
